JP4477478B2 - Optical pulse peak value control method for optical time division multiplexed signal - Google Patents

Description

  The present invention relates to a method for observing the peak value of an optical pulse constituting an optical time division multiplexed signal, and a method for controlling the peak value of an optical pulse based on the observed value. Moreover, it is related with the apparatus for implement | achieving these methods.

  Optical time division multiplex communication generates optical pulse signals in parallel, multiplexes them on the time axis and transmits them, and separates the multiplexed optical pulse signals that are the reverse operation of the transmitting side on the receiving side. The communication adopts a method of returning to the original parallel optical pulse signal.

  Hereinafter, the expression “optical pulse signal” is used only when it means an optical pulse train reflecting a binary digital electric signal obtained by optically modulating an optical pulse train and converting the electric pulse signal into an optical pulse signal. Shall. On the other hand, the expression “optical pulse train” is used to indicate a total of optical pulses arranged at regular intervals on the time axis (hereinafter also referred to as “time slots”).

  In optical fiber communication, it is necessary to increase the communication speed as much as possible in order to effectively use optical communication resources such as an optical fiber communication network. Here, the communication speed is a speed indicating how many bits of information can be transmitted / received per unit time, and is also referred to as a bit rate. In addition, it is necessary to increase the number of multiplexed optical pulse signals (the number of multiplexed channels).

Up to now, there has been disclosed an optical time division multiplexing apparatus devised so that multiplexing processing is possible even when the bit rate of the signal of each channel is different in relation to the technology for multiplexing optical pulse signals. (For example, see Patent Document 1). In addition, in an optical time division multiplexing apparatus that multiplexes an even number of channels, a two-multiplexed optical module is disclosed in which a device that does not cause noise superposition even when the multiplicity is increased is disclosed (for example, see Patent Document 2). .
Japanese Patent Laid-Open No. 7-123073 JP 2001-168844

  However, there is no optical time division multiplexing apparatus capable of realizing optical time division multiplexing by adjusting the peak values of the optical pulses constituting the optical signals of the multiplexed channels to be equal.

  If the peak values of the optical pulses that make up the optical signal of each channel to be multiplexed are different from each other, relatively large noise is mixed in the channel that is composed of optical pulses with low intensity (optical pulses with low peak values). It becomes a state. Therefore, it is important to adjust and transmit so that the peak values of the optical pulses constituting the optical signals of the multiplexed channels are all equal.

  Accordingly, a first object of the present invention is to provide a method capable of quantifying and observing the crest value of an optical pulse constituting an optical signal by a simple method and an apparatus for realizing the method. A second object of the present invention is to provide a method for controlling the peak values of the optical pulses constituting the optical signals of the multiplexed channels to be always equal to each other, and an apparatus for realizing the method. . A third object of the present invention is to provide a method for automatically controlling the crest values of optical pulses constituting the optical pulse signals of the multiplexed channels to be always equal to each other.

To achieve the first object above, a pulse peak value observed how a first invention, of the optical pulses constituting the optical time division multiplex signal used in the signal optical time division multi Shigemichi by synchronous detection A peak value observing method, comprising an optical pulse signal generation step, a peak value detection step, and a peak value data generation step. The optical pulse signal generation step is a step of generating an optical pulse signal by modulating an optical pulse train having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal with a modulation signal synchronized with the clock signal. The peak value detecting step is a step of detecting the peak value of the optical pulse constituting the optical pulse signal by converting it to a DC voltage signal proportional to the peak value of the optical pulse. The peak value data generation step corresponds to the difference between the reference voltage value set as the same value for all channels as the voltage value corresponding to the reference peak value and the DC voltage signal detected in the peak value detection step. In this step, the voltage value is generated as peak value data.

Light pulse peak value observation method is a peak value observation method of the optical pulses constituting the optical time division multiplex signal used in the signal optical time division multi Shigemichi by synchronous detection, the light pulse peak value observation apparatus of the present invention It is realized by. That is, the optical pulse peak value observation apparatus includes an optical pulse signal generation unit, a peak value detection unit, and a peak value data generation unit. The optical pulse signal generator generates an optical pulse signal by modulating an optical pulse train having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal with a modulation signal synchronized with the clock signal. Realize the step. The peak value detection unit realizes a peak value detection step in which the peak value of the optical pulse constituting the optical pulse signal is detected by converting it to a DC voltage signal proportional to the peak value of the optical pulse. The peak value data generation unit corresponds to the difference between the reference voltage value set as the same value for all channels and the DC voltage signal detected in the peak value detection step as the voltage value corresponding to the reference peak value. A peak value data generation step for generating a voltage value to be generated as peak value data is realized.

To achieve the second object above, a pulse peak value control method is a second aspect of the present invention, the optical pulses constituting the optical time division multiplex signal used in the signal optical time division multi Shigemichi by synchronous detection A crest value control method, comprising an optical pulse signal generation step, a crest value detection step, a crest value data generation step, and a crest value control step.

The optical pulse signal generating step is a step of generating an optical pulse signal for each N channel by modulating an optical pulse train having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal with a modulation signal synchronized with the clock signal. It is. The peak value detecting step is a step of detecting the peak value of the optical pulse constituting the optical pulse signal by converting it into a DC voltage signal for each N channel proportional to the peak value of the optical pulse. The peak value data generation step includes a reference voltage value set as the same value for all channels as a voltage value corresponding to the reference peak value, and a DC voltage signal for each N channel detected in the peak value detection step. This is a step of generating a voltage value for each N channel corresponding to the difference between and as peak value data. The peak value control step is a step of controlling the peak value of the optical pulse for each N channel constituting the optical pulse signal so that the peak value data for each N channel all have the same voltage value.

Light pulse peak value control method is a peak value control method of the optical pulses constituting the optical time division multiplex signal used in the signal optical time division multi Shigemichi by synchronous detection, the light pulse peak value control device of the present invention It is realized by. That is, the optical pulse peak value control device includes an optical pulse signal generation unit, a peak value detection unit, a peak value data generation unit, and a bias voltage control unit.

The optical pulse signal generation unit modulates an optical pulse train having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal with a modulation signal synchronized with the clock signal to generate an optical pulse signal for each N channel. A pulse signal generation step is executed. The peak value detection unit executes a peak value detection step of converting the peak value of the optical pulse constituting the optical pulse signal into a DC voltage signal for each N channel that is proportional to the peak value of the optical pulse. The peak value data generator generates the voltage value corresponding to the reference peak value for each N channel corresponding to the difference between the reference voltage value set as the same value for all channels and the DC voltage signal for each N channel. A peak value data generation step of generating the voltage value of the current as peak value data is executed. The bias voltage control unit has a peak value control step for controlling the peak value of the optical pulse for each of the N channels constituting the optical pulse signal so that the peak value data for each of the N channels are equal to each other. Execute. Here, N is a natural number of 2 or more.

To achieve the third object described above, the wave height value automatic control method for an optical pulse is a third aspect of the invention, light constituting the optical time division multiplex signal used in the signal optical time division multi Shigemichi by synchronous detection A pulse peak value automatic control method comprising the following first to ninth steps. That is,
First step: A temporary voltage value is set in a DC voltage setting circuit that supplies a DC bias voltage to a variable optical attenuator that superimposes a low-frequency modulation signal on an optical pulse signal.

  Second step: The peak value of the optical pulse signal is observed by the waveform monitor to determine whether or not the observed value is within the design value range. Returning to step 1, if the crest value is within the range of the design value, the DC voltage setting circuit is instructed to set the temporary voltage value as the initial voltage value.

  Third step: An initial voltage value is set in the DC voltage setting circuit.

Fourth step: First, output data output from the voltage output unit is input to the initial value data storage unit after completion of the third step.

Fifth step: Output data output from the voltage output unit after the third step is input to the data collecting unit after the second step.

Sixth step: The difference between the output data of the voltage output unit input to the data collection unit and the output data of the voltage output unit input to the initial value data storage unit is calculated as peak value data.

  Step 7: Determine whether the peak value data is positive or negative.

  Eighth step: If the peak value data is a negative value, the initial voltage value set in the DC voltage setting circuit is changed so that the optical loss amount of the variable optical attenuator decreases.

  Ninth step: If the peak value data is a positive value, the initial voltage value set in the DC voltage setting circuit is changed so that the optical loss amount of the variable optical attenuator increases.

  According to the optical pulse peak value observation method of the first invention, an optical pulse signal is generated in the optical pulse signal generation step, and in the peak value detection step, the peak value of the optical pulse is proportional to the peak value of the optical pulse. Converted to a DC voltage signal. That is, according to the optical pulse peak value observation method of the present invention, the peak value of the optical pulse is converted into a DC voltage signal and output.

  In the method of measuring the crest value of an optical pulse by observing the eye pattern of the optical pulse signal using a waveform monitor such as a conventional optical sampling oscilloscope, the crest value of the optical pulse is digitized without human intervention. It was difficult to do. However, according to the optical pulse peak value observation method of the present invention, since the peak value of the optical pulse is converted into a DC voltage signal and output, it can be quantified without human intervention. Then, it is possible to automatically control the crest value of the optical pulse based on the digitized value.

  According to the optical pulse peak value control method according to the second aspect of the present invention, in the peak value control step, each N channel constituting the optical pulse signal is configured such that the peak value data for each N channel are equal to each other. The peak values of the optical pulses are controlled. That is, as will be described in detail later, the bias voltage control unit that executes the peak value control step can control the peak value of the optical pulse to keep the peak value corresponding to the reference voltage value for each N channel. As a result, it is possible to establish a method for controlling so that the peak values of the optical pulses constituting the optical signal of each channel multiplexed in N channels are always equal to each other.

According to the optical pulse peak value automatic control method according to the third aspect of the present invention, whether the peak value data is positive or negative is determined by executing the first to ninth steps described above. The crest value data is automatically controlled so as to always be equal to 0. That is, the control is automatically performed so that the difference between the output data of the voltage output unit and the output data of the voltage output unit input to the initial value data storage unit is always equal to zero. As a result, the crest value of the optical pulse constituting the optical pulse signal of each channel is automatically controlled so as to always be equal to the crest value corresponding to the initial data, so that the optical signal of each multiplexed channel is constructed. It is possible to automatically control the crest values of the optical pulses so that they are always equal to each other. Further, the optical pulse peak value automatic control method according to the third invention can be applied to the optical pulse peak value control method according to the second invention described above.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Each figure shows one configuration example according to the present invention, and only schematically shows the arrangement relationship of each component to the extent that the present invention can be understood. It is not limited to. In the following description, specific equipment and conditions may be used. However, these materials and conditions are only one of preferred examples, and are not limited to these. Moreover, in each figure, the same component is shown with the same number, and the overlapping description may be omitted. In addition, an optical path is indicated by a thick line and an electric path is indicated by a thin line. The numbers given to the bold lines and the thin lines mean the optical signal and the electric signal propagating through the optical path and the electric path to which the numbers are attached, respectively.

<First embodiment>
With reference to FIG. 1, a first optical pulse peak value observation method and a first optical pulse peak value observation apparatus for realizing the method according to the first invention will be described. FIG. 1 is a schematic block diagram of the first optical pulse peak value observation apparatus.

  The optical pulse signal generation unit 50 modulates an optical pulse train 5 having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal with a modulation signal 7 synchronized with the clock signal, and performs RZ (Return to Zero) encoding. The optical pulse signal 11 that is the optical RZ signal thus generated is generated. The modulation signal 7 is a binary digital electric pulse signal. The optical pulse train 5 is generated by a mode-locked semiconductor laser or the like. That is, in the optical pulse signal generation unit 50, an optical pulse train having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal is modulated with a modulation signal synchronized with the clock signal, and an optical pulse signal is generated. An optical pulse signal generation step (hereinafter also referred to as “step A”) is executed.

  The modulated signal 7 synchronized with the clock signal is supplied from the modulated electrical signal generator 8 to the optical modulator 10. As the optical modulator 10, for example, an electro-absorption modulator (EAM) can be used. In the first embodiment, as will be described later, a tandem optical modulator in which an optical modulator 10 and a variable optical attenuator (VOA) 12 are integrally formed is used.

  Depending on the modulation signal 7 supplied from the modulation electric signal generator 8, the optical modulator 10 is in a transmission state or a cutoff state. That is, it becomes opaque while a reverse bias voltage is applied to the EAM constituting the optical modulator 10, and becomes transparent as the reverse bias voltage decreases. That is, EAM is a transmission window that becomes transparent or opaque according to the modulation signal 7.

  By inputting the optical pulse train 5 to the optical modulator 10, only the optical pulse that has passed through the transmission window is filtered and output from the optical modulator 10 as the optical pulse signal 11. That is, the optical pulse signal generation unit 50 generates an optical pulse signal by modulating an optical pulse train having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal with a modulation signal synchronized with the clock signal. Implement the pulse signal generation step (Step A).

  Next, the peak value detection step will be described. Hereinafter, the peak value detection step may be referred to as “step B”. Step B includes the following steps B1 to B5.

  That is, step B1: superimposing the low frequency modulation signal 27 corresponding to the sum of the DC bias voltage and the modulation signal having a frequency lower than the frequency of the clock signal on the optical pulse signal 11 generated in the optical modulator 10 described above. A step of generating a low-frequency superimposed optical pulse signal 13; a step B2: a step of photoelectrically converting the low-frequency superimposed optical pulse signal 13 into an electrical pulse signal 17; and a step B3: extracted from the electrical pulse signal 17 Extracting a low-frequency modulation component 19 that is a frequency component equal to the low-frequency modulation signal; and step B4: mixing the low-frequency modulation component 19 and the low-frequency modulation signal 29 to generate a mixing signal 21; Step B5: A step in which high frequency components are removed from the mixing signal 21 and converted to a DC voltage signal 33 proportional to the peak value of the optical pulse constituting the optical pulse signal for detection. It is with the top.

  The peak value detecting unit 48 for realizing the peak value detecting step includes a VOA 12, a photoelectric converter 16, a first filter 18, a mixer 20, and a second filter 32. The first filter 18 can use a low-pass filter (LPF). Since the electrical pulse signal 17 may contain a frequency component lower than the low-frequency modulation component 19, in this case, a band-pass filter (BPF: Band-Pass Filter) that transmits only the low-frequency modulation component 19 Is preferably used. Since the role of the second filter 32 is to extract the DC voltage signal 33, it is preferable to use LPF, and BPF cannot be used.

  Then, the peak value detection unit 48 converts the peak value of the optical pulse constituting the optical pulse signal 11 into a DC voltage signal proportional to the peak value of the optical pulse and outputs it as a DC voltage signal 33. That is, the peak value of the optical pulse constituting the optical pulse signal 11 is detected by being converted into a DC voltage signal having a magnitude proportional to the peak value.

  The optical pulse signal 11 output from the optical pulse signal generation unit 50 is input to the VOA 12. The VOA 12 has a low frequency equivalent to the sum of the DC bias voltage signal 23 supplied from the DC voltage setting circuit 22 and the modulation signal ((RF: Radio Frequency) signal) 25 supplied from the low frequency signal generator 24. A modulation signal 27 is input. That is, the VOA 12 superimposes the low frequency modulation optical pulse signal 13 on the optical pulse signal 11 by superimposing the low frequency modulation signal 27 corresponding to the sum of the DC bias voltage and the modulation signal having a frequency lower than the frequency of the clock signal. The outputting step (Step B1) is realized.

  2A to 2C, the optical pulse signal 11 is input to the VOA 12, and the low frequency modulation signal corresponding to the sum of the DC bias voltage and the modulation signal having a frequency lower than the frequency of the clock signal. Steps until 27 is superimposed and output as the low-frequency superimposed optical pulse signal 13 will be described. 2A to 2C, the time axis is scaled with an arbitrary scale. 2A and 2C, the vertical axis indicates the light intensity, and the vertical axis in FIG. 2B indicates the voltage on an arbitrary scale.

FIG. 2 (A) schematically shows the optical pulse signal 11. An optical pulse constituting the optical pulse signal 11 is approximately represented by a line segment parallel to the vertical axis. Actually, it is an optical pulse signal composed of an optical pulse having a finite half-value width encoded by RZ, and is a binary digital signal modulated by an electric pulse signal. In FIG. 2A, for the sake of simplicity, a state in which an optical pulse is present in all the time slots is shown, but there are actually time slots in which no optical pulse exists. The time slot interval is labeled t. In FIG. 2 (A), the intensity of the light pulses is all equal. For convenience of the following description, the intensity of the light pulse shown in FIG. 2 (A) and I _0.

FIG. 2 (B) schematically shows the low frequency modulation signal 27. The period T of the low frequency modulation signal 27 is set sufficiently larger than the time slot interval t. That is, the low frequency modulation signal 27 has a frequency (1 / T) that is sufficiently lower than the frequency (1 / (2t)) of the clock signal of the optical pulse signal 11. The VOA 12 receives a low frequency modulation signal 27 corresponding to the sum of the DC bias voltage signal 23 supplied from the DC voltage setting circuit 22 and the low frequency RF signal 25 supplied from the low frequency signal generator 24. The FIG. 2B shows the DC bias voltage supplied from the DC voltage setting circuit 22 as Vb, and the amplitude of the RF signal supplied from the low frequency signal generator 24 as V _p / 2.

FIG. 2C schematically shows the low-frequency superimposed optical pulse signal 13. The modulation intensity (the magnitude of the modulation component) received by the optical pulse signal 11 by the low frequency modulation signal 27 is expressed as I _p . In the first embodiment, the frequency (1 / T) of the low frequency modulation signal 27 is 1 kHz. The modulation intensity I _p received by the optical pulse signal 11 was set to 1 dB or less, and the amplitude I _p / 2 of the modulation intensity received by the optical pulse signal 11 was set to 0.5 dB or less.

If the modulation intensity I _p received by the optical pulse signal 11 is too large, an influence such as affecting the waveform of the optical pulse constituting the optical pulse signal appears. Therefore, the modulation intensity I _p is smaller than the intensity I of the optical pulse. It is desirable to be as small as possible. On the other hand, in the step of generating the mixing signal 21 by mixing the low frequency modulation component 19 extracted from the electric pulse signal 17 and the low frequency modulation signal 29 output via the phase adjuster 30 by the mixer 20. It is desirable that the modulation intensity I _p is as large as possible.

Therefore, how much the modulation intensity I _p is set belongs to the design matter of the optical time division multiplexing optical communication system in which the first optical pulse peak value observation apparatus of the present invention is used. That is, the value is set to a value at which the mixing step can be executed within a range that does not affect the waveform of the optical pulse constituting the optical pulse signal.

The modulation component magnitude I _{p of} the low-frequency superimposed optical pulse signal 13 shown in FIG. 2 (C), the modulation component magnitude V _{p of} the low-frequency modulation signal 27 shown in FIG. There is a relationship given by the following equation (1) with the intensity I ₀ of the optical pulse signal 11 shown in FIG.
I _p = K x I ₀ x V _p (1)
Here, K is a constant and is a value depending on the DC bias voltage supplied from the DC voltage setting circuit 22, the optical attenuation characteristic of the VOA 12, and the like. That is, the magnitude I _p of the modulation component of the low frequency superimposed optical pulse signal 13 is proportional to the intensity I ₀ of the optical pulse signal 11.

  The frequency (1 / T) of the low frequency modulation signal 27 is set according to the bit rate of the optical time division multiplexing optical communication system in which the first optical pulse peak value observation apparatus of the present invention is used. That is, the frequency (1 / T) of the low frequency modulation signal 27 is a frequency that can pass through the first and second filters used in the present invention, and the first and second filters. However, it is a condition that a high frequency component corresponding to the bit rate can be cut off.

  As described above, the VOA 12 superimposes the low frequency modulation signal 27 corresponding to the sum of the DC bias voltage signal 23 and the modulation signal 25 having a frequency lower than the frequency of the clock signal on the optical pulse signal 11. Output as superimposed light pulse signal 13.

  The low-frequency superimposed optical pulse signal 13 is generated by the low-frequency modulation signal 27 corresponding to the sum of the DC bias voltage supplied from the DC voltage setting circuit 22 and the RF signal 25 supplied from the low-frequency signal generator 24. 11 is modulated. The low frequency superimposed optical pulse signal 13 is divided by the optical splitter 14 into a low frequency superimposed optical pulse signal 13a and a low frequency superimposed optical pulse signal 13b. One low-frequency superimposed optical pulse signal 13b becomes a transmitted optical pulse signal, and the other low-frequency superimposed optical pulse signal 13a is used as a signal for detecting the peak value of the optical pulse.

  For the convenience of the following description, the optical pulse signal generation is performed on the portion including the modulated electric signal generator 8, the optical modulator 10, and the VOA 12 where the optical pulse train 5 is input and the low-frequency superimposed optical pulse signal 13 is output. It may also be called a modulation unit 51.

  The photoelectric converter 16 executes Step B2 in which the low-frequency superimposed optical pulse signal 13a on which the low-frequency modulation signal 27 is superimposed is photoelectrically converted into an electric pulse signal 17.

  The first filter 18 receives the electric pulse signal 17, removes a high frequency component of the electric pulse signal 17, that is, a frequency component sufficiently higher than the frequency of the low frequency modulation signal 27, and has a frequency component equal to the low frequency modulation signal 27. Step B3 of outputting the low frequency modulation component 19 is executed.

  The mixer 20 mixes the low frequency modulation component 19 having the same frequency component as the low frequency modulation signal 27 extracted from the electrical pulse signal 17 and the low frequency modulation signal 29 to generate a mixing signal 21 in step B4. Execute. The low frequency modulation signal 29 is a phase adjuster in which the low frequency RF signal 25 output from the low frequency signal generator 24 is branched into the RF signal 25a and the RF signal 25b by the branching device 28. 30, the phase of which is adjusted. The phase of the low frequency modulation signal 29 is adjusted by the phase adjuster 30 so as to match the phase of the low frequency modulation component 19. The RF signal 25 a becomes a low frequency modulation signal 27 corresponding to the sum of the DC bias voltage signal 23 output from the DC voltage setting circuit 22 by the combiner 26 and is supplied to the VOA 12.

  The second filter 32 executes step B5 by removing high frequency components from the mixing signal 21 and converting it to a DC voltage signal 33 proportional to the peak value of the optical pulse constituting the low frequency superimposed optical pulse signal 13. For convenience of the following description, the DC voltage signal extraction unit is a part that inputs the low frequency modulation component 19 and the RF signal 25b and extracts the DC voltage signal 33, which includes the mixer 20, the phase adjuster 30, and the second filter 32. 178.

  A low frequency modulation component 19 having a frequency component equal to the frequency of the low frequency modulation signal 27 and a low frequency modulation signal 29 are input to the mixer 20. The low frequency modulation signal 29 is one RF modulation signal 25b obtained by branching the RF modulation signal 25 supplied from the low frequency signal generator 24 into two by the branching device 28, and the phase of the RF modulation signal 25 is adjusted by the phase adjuster 30. Signal. The other input signal, the low frequency modulation component 19, is extracted from the low frequency superimposed light pulse signal 13. The low-frequency superimposed optical pulse signal 13 is optically pulsed by a low-frequency modulation signal 27 corresponding to the sum of an RF modulation signal 25a and a DC bias voltage signal 23 that are part of an electrical signal supplied from the low-frequency signal generator 24. The signal 11 is modulated and output from the variable optical attenuator 12.

  Accordingly, the low frequency modulation component 19 and the low frequency modulation signal 29 have the same frequency. If the phase of the low-frequency modulation component 19 and the phase of the low-frequency modulation signal 29 match, the mixing signal 21 output from the mixer 20 becomes a DC signal. Therefore, if the high frequency noise component is removed from the mixing signal 21 by the second filter 32, the peak value can be converted and observed as a voltage signal proportional to the peak value with high sensitivity.

The magnitude of the mixing signal 21, which is a DC signal obtained by matching the phase of the low frequency modulation component 19 with the phase of the low frequency modulation signal 29, is the magnitude of the modulation component of the low frequency superimposed optical pulse signal 13 described above. Proportional to I _p . Further, as described above, the magnitude _Ip of the modulation component of the low-frequency superimposed optical pulse signal 13 is proportional to the intensity of the optical pulse I ₀ , so the magnitude of the mixing signal 21 is equal to the intensity I of the optical pulse signal 11. There is a relationship proportional to _zero .

  The above-described phase adjuster 30 performs adjustment for matching the phase of the low frequency modulation component 19 with the phase of the low frequency modulation signal 29. The phase adjuster 30 maximizes the DC component of the mixing signal 21 output from the mixer 20, with the phase of the RF signal 25b branched from the RF signal 25 supplied from the low-frequency signal generator 24 by the branching device 28. Adjust as follows.

  The relationship between the phase of the low-frequency modulation component 19 and the phase of the low-frequency modulation signal 29 does not change unless the peak value detection unit 48 is changed, such as by changing the components constituting the peak value detection unit 48. Therefore, once this adjustment is performed, it is not necessary to change the component parts constituting the peak value detection unit 48 unless the peak value detection unit 48 is changed.

  Step B5 executed by the second filter 32 is a step for removing the high frequency component from the mixing signal 21 to obtain the DC voltage signal 33. That is, this step is provided to remove the uncertainty of the mixing signal 21 detected by the peak value detector 48 due to high-frequency noise mixed in the DC voltage signal 33.

As is clear from the above, if the phase of the low frequency modulation component 19 and the phase of the low frequency modulation signal 29 match, the magnitude of the DC voltage signal 33 is equal to the magnitude of the DC component of the mixing signal 21. It is proportional to the depth. Therefore, it can be seen that the magnitude of the DC voltage signal 33 is proportional to the intensity I _{0 of the} optical pulse. In other words, in step B5, the magnitude of the DC voltage signal 33 obtained by removing the high frequency component from the mixing signal 21 is proportional to the peak value of the optical pulse constituting the optical pulse signal.

  The crest value detecting step can be realized other than step B including steps B1 to B5 described above. Next, an example will be described in which the peak value detection step is realized with a configuration that is partially different from Step B described above.

  With reference to FIG. 3, the first optical pulse peak value observation method adopting step B comprising steps B1 to B5 described above and the first optical pulse peak value observation apparatus for realizing this method are different. The second optical pulse peak value observation method and the second optical pulse peak value observation apparatus will be described. FIG. 3 is a schematic block diagram of the second optical pulse peak value observation apparatus.

  In the peak value observation of the first optical pulse, the low frequency modulation component 19 extracted from the electric pulse signal 17 is generally weaker than the low frequency modulation signal 29 output via the phase adjuster 30. It is. Therefore, it may be assumed that the above-described step (Step B4) of generating the mixing signal by mixing the low-frequency modulation component and the low-frequency modulation signal cannot be performed well.

  Therefore, a second optical pulse peak value observation method in which the above-described step B4 is changed as follows and a second optical pulse peak value observation apparatus capable of realizing this method were completed.

  That is, the steps corresponding to the above-described steps B4 and B5 include steps B4-1 to B5-2 shown below. In Step B of the second optical pulse peak value observation method, Step B1 to Step B3 of the first optical pulse peak value observation method described above are common to the steps in Step B of the second optical pulse peak value observation method. Therefore, the component parts of the apparatus for realizing these steps and the description thereof are omitted here. Since step A is common to both, the same description is omitted.

  Step B4 includes the following steps B4-1 to B4-3. That is, step B4-1: a step of bifurcating the low frequency modulation component into a first low frequency modulation component and a second low frequency modulation component, and step B4-2: the first low frequency modulation component and the low frequency Mixing the modulation signal to generate a first mixing signal; and step B4-3: delaying the phase of the low-frequency modulation signal by 90 ° to generate a 90 ° -delayed low-frequency modulation signal and generating a second low-frequency modulation component And a 90 ° delayed low frequency modulation signal to generate a second mixing signal.

  Step B5 includes Step B5-1 and Step B5-2 shown below. That is, step B5-1: removing the high frequency component from the first mixing signal and the second mixing signal, respectively, and the first voltage value and the second voltage value proportional to the peak value of the optical pulse constituting the optical pulse signal, respectively. And a step B5-2: generating a DC voltage signal that is a mean square value of the first voltage value and the second voltage value as a DC voltage signal.

  The branching device 52 executes Step B4-1 in which the low-frequency modulation component 19 is bifurcated into a first low-frequency modulation component 19a and a second low-frequency modulation component 19b. The low frequency modulation signal 25b is branched into two by the branching unit 140, one of which is supplied as the low frequency modulation signal 59 to the first mixer 54, and the other is supplied to the 90 ° phase delay unit 58. The low-frequency modulation signal branched into two by the branching device 140 and supplied to the 90 ° phase delay device 58 is delayed by 90 ° by the 90 ° phase delay device 58 and is delayed as the second low-frequency modulation signal 141 by the second mixer 56. To be supplied.

  The first mixer 54 executes Step B4-2 in which the first low-frequency modulation component 19a and the low-frequency modulation signal 59 are mixed to generate the first mixing signal 55. The second mixer 56 generates a second mixing signal 57 by mixing the second low frequency modulation component 19b and the delayed low frequency modulation signal 141 delayed by 90 ° with respect to the phase of the low frequency modulation signal 25b. Execute B4-3.

  The third filter 142 and the fourth filter 144 remove the high frequency components from the first mixing signal 55 and the second mixing signal 57, respectively, and a first voltage value 143 proportional to the peak value of the optical pulse constituting the optical pulse signal. And Step B5-1 for conversion into the second voltage value 145, respectively. Since the third filter 142 and the fourth filter 144 are responsible for extracting the DC voltage signal 143 and the DC voltage signal 145, respectively, it is preferable to use LPF, and BPF cannot be used.

  The mean square value generation unit 146 executes Step B5-2 to generate a DC voltage signal 147 that is a mean square value of the first voltage value 143 and the second voltage value 145.

  The low frequency modulation component 19 output from the first filter 18 is an electric signal having a frequency component equal to the low frequency modulation signal 27. The low-frequency modulation component 19 is branched into a first low-frequency modulation component 19a and a second low-frequency modulation component 19b by the branching device 52, and supplied to the first mixer 54 and the second mixer 56, respectively. Therefore, the first low-frequency modulation component 19a and the second low-frequency modulation component 19b are electrical signals having frequency components equal to the low-frequency modulation signal 27.

  On the other hand, the RF modulation signal 25 supplied from the low frequency signal generator 24, which is supplied to the first mixer 54, is bifurcated by the splitter 28. Are equal. The delayed low frequency modulation signal 141 supplied to the second mixer 56 is a modulation signal whose phase is delayed by 90 ° compared to one of the low frequency modulation signals 59.

  A high frequency component is removed from the output first mixing signal 55 of the first mixer 54 by the third filter 142, and the first voltage value 143 is supplied to the mean square value generation unit 146. In addition, the high frequency component of the output second mixing signal 57 of the second mixer 56 is removed by the fourth filter 144, and the second voltage value 145 is supplied to the root mean square value generator 146. Then, the mean square value generation unit 146 generates a DC voltage signal 147 that is a mean square value of the first voltage value 143 and the second voltage value 145.

  Therefore, the branching device 52, the first mixer 54, the second mixer 56, the 90 ° phase delay device 58, the branching device 140, the third filter 142, the fourth filter 144, and the mean square value generator 146 shown in FIG. The provided two-phase lock-in amplifier unit 180 is a signal extraction device using a two-phase lock-in amplifier system. That is, in the two-phase lock-in amplifier unit 180, the DC voltage signal 147 proportional to the peak value of the optical pulse constituting the low-frequency superimposed optical pulse signal 13 is extracted from the low-frequency modulation component 19 by the two-phase lock-in amplifier method. .

  The two-phase lock-in amplifier unit 180 of the second optical pulse peak observation device corresponds to the DC voltage signal extraction unit 178 of the first optical pulse peak observation device.

  As described above, since the DC voltage signal 147 is extracted by the two-phase lock-in amplifier method, the DC voltage signal 147 is stably generated without depending on the phase relationship between the low frequency modulation component 19 and the low frequency modulation signal 25b. It is possible to extract. This eliminates the need for the phase adjuster 30 that was necessary in the first optical pulse peak value observation apparatus. Further, the extraction sensitivity of the DC voltage signal 147 can be improved by adopting the two-phase lock-in amplifier system.

  Therefore, even if the low-frequency modulation component 19 extracted from the electrical pulse signal 17 is weak, the step of generating the mixing signal by mixing the low-frequency modulation component and the low-frequency modulation signal (step B4) without any trouble It becomes possible to execute.

  Next, the peak value data generation step will be described. Hereinafter, the peak value data generation step may be referred to as “step C”. Step C includes steps C1 to C3 shown below.

That is, step C1: setting a reference voltage value, step C2: collecting a DC voltage signal corresponding to the peak value of the optical pulse constituting the optical pulse signal generated in the peak value detecting step, and step C3 : Generating a voltage value corresponding to the difference between the collected DC voltage signal and the reference voltage value as peak value data.

  With reference to FIG. 1 and FIG. 3, the configuration of peak value data generation unit 46 and their functions will be described. The configuration of the peak value data generation unit 46 of the first optical pulse peak value observation apparatus shown in FIG. 1 and the second optical pulse peak value observation apparatus shown in FIG. 3 are the same. Therefore, the description will mainly be given with reference to FIG. 1, and the peak value detection unit that performs a common function in both drawings will be described with reference to the peak value detection unit 48 in FIG. The description of the high value detection unit 148 is omitted.

  The peak value detector 48 in FIG. 1 corresponds to the peak value detector 148 in FIG. 2, and the DC voltage signal 33 output from the second filter 32 in FIG. 1 is a mean square value generator 146 in FIG. This corresponds to the DC voltage signal 147 output from.

The peak value data generation unit 46 for realizing the peak value data generation step includes an initial value data storage unit 42, a data collection unit 36, and a data processing unit 38. Further, a control unit 44 for controlling the initial value data storage unit 42, the data collection unit 36, and the data processing unit 38 is provided. The peak value data generating unit 46 outputs a voltage value corresponding to the difference between the reference voltage value and the DC voltage signal 33 output from the peak value detecting unit 48 as the peak value data 47.

The initial value data storage unit 42 executes Step C1 for storing a reference voltage value set as a voltage value corresponding to the reference peak value. The data collecting unit 36 executes Step C2 in which a DC voltage signal that is proportional to the peak value of the optical pulse that constitutes the low-frequency superimposed optical pulse signal 13 generated in the peak value data generating step is collected . The data processing unit 38 executes Step C3 in which a voltage value corresponding to the difference between the DC voltage signal collected in Step C2 and the reference voltage value is generated as peak value data.

  First, the DC voltage signal 33 output from the second filter 32 is connected to the input terminal of the initial value data storage unit 42 by connecting the output terminal of the second filter 32 as indicated by a broken line in FIG. The data is input to the unit 42. Then, the initial value data storage unit 42 is output from the second filter 32 in a state where the peak value of the optical pulse constituting the low-frequency superimposed optical pulse signal 13 obtained in advance by a waveform monitor or the like takes a desirable value. The voltage value of the DC voltage signal 33 (hereinafter also referred to as “initial voltage value”) is stored.

Next, the output terminal of the second filter 32 is input to the data collection unit 36 so that the DC voltage signal 33 output from the second filter 32 is input to the data collection unit 36 instead of the initial value data storage unit 42. Reconnect to the terminal. After this, the DC voltage signal 33 output from the second filter 32 is sequentially sent to the data processing unit 38 as the DC voltage signal 37. The data processing unit 38 compares the value of the DC voltage signal 33 output from the second filter 32 with the initial voltage value 43 output from the initial value data storage unit 42 to determine the magnitude thereof, and the DC voltage signal 33 When the value of is large, a positive value is output, and when it is small, a negative value is output. That is, the data processing unit 38 outputs the difference between the DC voltage signal 37 and the initial voltage value 43 supplied from the initial value data storage unit 42.

The control unit 44 instructs the execution of step C1 to store the reference voltage value set as the voltage value corresponding to the reference peak value in the initial value data storage unit 42. Further, by controlling the data collection unit 36 collects a DC voltage signal proportional to the peak value of the optical pulses constituting the low-frequency superimposing optical pulse signal 13 generated by the amplitude data generating step, the execution of the steps C2 Instruct. Further, the data processing unit 38 is controlled to instruct execution of step C3 to generate a voltage value corresponding to the difference between the DC voltage signal collected in step C2 and the reference voltage value as peak value data.

  If the value of the DC voltage signal 33 output from the second filter 32 is larger than the initial voltage value, it means that the peak value of the optical pulse corresponding to the voltage value set as the initial voltage value is large. Conversely, if it is smaller than the initial voltage value, it means that the peak value of the optical pulse corresponding to the voltage value set as the initial voltage value is small. Therefore, the peak value data generated in step C3 is a signal indicating whether the peak value of the optical pulse constituting the low-frequency superimposed optical pulse signal 13 is smaller or larger than the reference peak value. From this peak value data, it is possible to know how much the peak value of the optical pulse constituting the low frequency superimposed optical pulse signal 13 is deviated from the reference peak value with respect to the reference peak value.

  As described above, according to the optical pulse peak value observation method of the first invention, it is possible to digitize the peak value of the optical pulse without human intervention. Maintenance of the optical time division multiplexing communication system can be automated by a machine using the peak value data output from the unit as an index.

<Tandem type optical modulator>
A specific configuration example of the EAM and VOA 12 that are the optical modulator 10 will be described with reference to FIG. In the first embodiment, a tandem type optical modulator in which the optical modulator 10 and the VOA 12 are integrally formed is used. FIG. 4 is a schematic configuration diagram of a tandem optical modulator. The tandem light modulation element 240 includes a light guide 236, and is a diode having a PN junction set at a position where the light guide 236 is formed.

  The tandem type light modulation element 240 is sandwiched between the first light absorption region 230 and the second light absorption region 232, and a waveguide region 234 is formed. That is, the tandem type optical modulation element 240 has an optical pulse train 5 having a repetition frequency equal to the frequency of the clock signal from the left side as viewed in the drawing and is synchronized with the clock signal as incident light. In this configuration, the low-frequency superimposed light pulse signal 13 on which the signal 27 is superimposed is output as emitted light. Antireflection films 226 and 228 are respectively formed on the incident end face on the left side in the drawing and the emission end face on the right side in the drawing.

  In the present invention, the first light absorption region 230 functions as the EAM that is the optical modulator 10, and the second light absorption region 232 functions as the VOA 12. The modulation electric signal generation unit 8 includes a coil 208, a modulation electric signal supply unit 206, a bias power supply 210, and a capacitor 204. The coil 208 is inserted to prevent the AC component of the electrical signal supplied from the modulated electrical signal supply unit 206 from being input to the bias power supply 210. The capacitor 204 is inserted to prevent a bias voltage (DC voltage) supplied from the bias power source 210 from being input to the modulated electric signal supply unit 206.

  In general, if no voltage is applied to the first light absorption region 230, the optical waveguide of the first light absorption region 230 may be considered transparent to input light. Actually, the light absorption coefficient of the optical waveguide of the first light absorption region 230 with respect to the input light is not zero, but here, for the sake of simplicity, the light absorption coefficient will be described as being zero. On the other hand, if the potential on the P pole side of the first light absorption region 230 is set lower than the potential on the N pole side, the light absorption coefficient of the optical waveguide of the first light absorption region 230 with respect to input light increases as the potential difference increases. And it becomes opaque.

  Further, when a forward voltage is applied to the first light absorption region 230, the first light absorption region 230 operates as a light emitting diode, and in this case, the input light input to the first light absorption region 230 Furthermore, since light emitted as a light emitting diode is added and output, it cannot be used as an optical modulator. Therefore, the bias voltage applied to the first light absorption region 230 is the potential on the P pole side of the first light absorption region 230 even at the moment when the maximum value of the modulated electric signal is input to the first light absorption region 230. Must be set lower than the potential on the N pole side.

  As shown in FIG. 4, a reverse potential is applied to the diode via the coil 208 by the bias power supply 210. That is, the potentials of the P-side electrodes 212a and 212b are set lower than the potential of the N-side electrode 214.

  Further, as shown in FIG. 4, a modulated electrical signal synchronized with the clock signal is supplied from the modulated electrical signal supply unit 206, and the modulated electrical signal generating unit 8 is connected to the P side via the capacitor 204 as the modulated signal 7. Supplied to the electrode 212a. As a result, the modulated signal 7 synchronized with the clock signal is supplied from the modulated electric signal generator 8 to the optical modulator 10.

  On the other hand, in the present invention, the second light absorption region 232 is made to function as the VOA 12. A low frequency modulation signal 27 corresponding to the sum of the DC bias voltage 23 supplied from the DC voltage setting circuit 22 and the RF signal 25 supplied from the low frequency signal generator 24 is input to the second light absorption region 232. The That is, the low frequency modulation signal 27 is configured to be supplied to the P-side electrode 212b. Further, the sum of the DC bias voltage 23 supplied from the DC voltage setting circuit 22 and the RF signal 25 supplied from the low frequency signal generator 24 is applied to the P-side electrode 212b of the second light absorption region 232 corresponding to VOA 12. A low-frequency modulation signal 27 corresponding to is applied. As a result, when the optical pulse signal 11 is input to the second optical absorption region 232, the optical pulse signal 11 has a low frequency equivalent to the sum of a DC bias voltage and a modulation signal having a frequency lower than the frequency of the clock signal. A low-frequency superimposed optical pulse signal 13 on which the modulation signal 27 is superimposed is output.

  Again, as in the modulated electrical signal generator 8, a coil is inserted to prevent the RF signal 25 supplied from the low frequency signal generator 24 from being input to the DC voltage setting circuit 22, and the DC voltage setting circuit A capacitor is inserted to prevent the bias voltage (DC voltage) 23 supplied from 22 from being input to the low frequency signal generator 24, but is omitted in FIG.

<Second Embodiment>
With reference to FIG. 5, an optical pulse peak value control method and an optical pulse peak value control apparatus for realizing the method according to the second invention will be described. FIG. 5 is a schematic block diagram of the optical pulse peak value control apparatus. Here, a case of optical time division multiplexing in which optical pulse signals for two channels are multiplexed will be described as an example. Of course, the optical pulse peak value control method of the present invention and the apparatus for realizing this method are not limited to the case of two-channel multiplexing, and can be similarly realized in the case of optical time-division multiplexing of three or more channels. .

  It should be noted that the optical modulator, variable optical attenuator, low frequency signal generator, DC voltage setting circuit, phase adjuster, photoelectric converter, filter, used in the optical pulse peak value control device of the second embodiment Since the components such as the mixer, the optical branching device, the merger, and the branching device can be the same as those used in the optical pulse peak value observation apparatus according to the first embodiment, these components are related to each other. Description is omitted.

  Since the optical pulse peak value control device shown in FIG. 5 is a two-channel optical time division multiplexing device, two optical pulse signal generation modulation units and two DC voltage signal extraction units are provided. That is, the optical pulse signal generation modulation unit includes two locations, the first channel optical pulse signal generation modulation unit 170 and the second channel optical pulse signal generation modulation unit 172, and the DC voltage signal extraction unit includes the first channel DC The voltage signal extracting unit 174 and the DC voltage signal extracting unit 176 of the second channel are two places.

  In order to support optical time division multiplexing of 3 channels or more, it is only necessary to install as many optical pulse signal generation modulation units and DC voltage signal extraction units as the number of channels.From the description of the 2-channel optical time division multiplexing device described below, A person skilled in the art can easily cope with optical time division multiplexing of three or more channels.

  The optical pulse peak value control apparatus includes an optical pulse signal generation unit 60, a peak value detection unit 100, a peak value data generation unit 130, and a bias voltage control unit 134.

  The optical pulse signal generation unit 60 includes a first channel optical pulse signal generation unit 161 and a second channel optical pulse signal generation unit 163. An optical pulse train 55 having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal is divided into two by the first optical demultiplexer 62 into an optical pulse train 61 and an optical pulse train 63, respectively. The pulse signal generator 161 and the second channel optical pulse signal generator 163 are supplied. In the case of an N-channel optical time division multiplexing device, an optical demultiplexer that can divide the optical pulse train 5 into N is used as the first optical demultiplexer 62.

  In the optical pulse signal generation unit 161 of the first channel, one optical pulse train 61 of the optical pulse train 55 divided into two by the electrical modulation signal supplied from the modulation electrical signal generation unit 66 to the optical modulator 64 is converted into an optical RZ signal ( Optical pulse signal) 65. Further, in the optical pulse signal generation unit 163 of the second channel, one optical pulse train 63 of the optical pulse train 55 divided into two by the electrical modulation signal supplied from the modulated electrical signal generation unit 70 to the optical modulator 68 is converted into the optical RZ. Generated as signal 69.

  That is, in the case of an N-channel optical time division multiplexing device, the optical pulse signal generator modulates an optical pulse train having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal with a modulation signal synchronized with the clock signal. Then, an optical pulse signal generation step for generating an optical pulse signal for each N channel is executed. This optical pulse signal generation step is a step corresponding to step A in the optical pulse peak value observation method according to the first invention. Hereinafter, this step is also referred to as Step A as long as no confusion occurs.

  As described above, the optical pulse signal generation unit 60 modulates an optical pulse train having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal with the modulation signal synchronized with the clock signal, for each N channel. An optical pulse signal generation step (step A) for generating an optical pulse signal is executed.

  Next, the peak value detection step will be described. The peak value detecting step includes the following steps B1 to B5.

  This peak value detection step is a step corresponding to step B in the optical pulse peak value observation method according to the first invention. Similarly, steps B1 to B5 are steps corresponding to steps B1 to B5 in the optical pulse peak value observation method according to the first invention. Hereinafter, within the range where no confusion occurs, the steps in the first invention and the second invention are not distinguished from each other and are referred to as step B or steps B1 to B5.

  Step B: Step B1: For each N channel, the optical pulse signal for each N channel corresponds to the sum of the DC bias voltage for each N channel and the modulation signal having a different frequency for each N channel that is lower than the frequency of the clock signal. A step of generating a low-frequency superimposed optical pulse signal by superimposing different low-frequency modulated signals on and B2: an optical pulse signal obtained by photoelectrically converting an optical pulse signal obtained by N-channel multiplexing of a low-frequency superimposed optical pulse signal for each N channel. Step to convert to pulse signal; Step B3: Extract low frequency modulation component that is equal to low frequency modulation signal from electrical pulse signal; Step B4: Mix low frequency modulation component and low frequency modulation signal Step to generate a mixing signal for each N channel, and step B5: remove high frequency components from the mixing signal. , And a step of converting a DC voltage signal for each N-channel that is proportional to the peak value of the optical pulses constituting the optical pulse signal.

  Since the optical pulse peak value control device shown in FIG. 5 is a two-channel optical time division multiplexing device, the above-mentioned N is an example corresponding to 2. The first channel optical pulse signal generation modulation unit 170 and the second channel optical pulse signal generation modulation unit 172 are the optical pulse signals of the optical pulse peak value observation apparatus of the first invention shown in FIG. 1 and FIG. This is a part corresponding to the generation modulation unit 51. The first-channel DC voltage signal extraction unit 174 and the second-channel DC voltage signal extraction unit 176 are the same as the DC voltage signal extraction unit 178 of the optical pulse peak value observation apparatus according to the first aspect shown in FIG. It corresponds to. That is, since there are two channels, two optical pulse signal generation modulation units and two DC voltage signal extraction units are provided.

  The peak value detection unit 100 for realizing the peak value detection step (step B) will be described separately for a part related to the first channel and a part related to the second channel. Portions common to both channels will be described with respect to portions related to the first channel, and description of overlapping portions related to the second channel will be omitted.

  First, the components for realizing step B1 for the first channel in the peak value detection unit 100 will be described. The first-channel optical pulse signal 65 output from the optical modulator 64 of the optical pulse signal generation unit 60 is input to the VOA 72. The VOA 72 receives a low frequency modulation signal 119 corresponding to the sum of the DC bias voltage 113 supplied from the DC voltage setting circuit 112 and the modulation signal 115 supplied from the low frequency signal generator 110. That is, the VOA 72 superimposes the low-frequency modulation signal 119 corresponding to the sum of the DC bias voltage and the modulation signal having a frequency lower than the frequency of the clock signal on the optical pulse signal 65, and the low-frequency superimposed light of the first channel The step of outputting the pulse signal 73 (Step B1) is realized.

  On the other hand, for the second channel, an optical delay device 76 is further added to the component for realizing Step B1 for the first channel. The optical delay unit 76 bit-interleaves the low-frequency superimposed optical pulse signal 75 of the second channel with the low-frequency superimposed optical pulse signal 73 of the first channel to generate a double multiplexed time-division multiplexed optical pulse signal 81. In addition, it is installed between the VOA 74 and the optical multiplexer 80.

  Bit interleaving is one of means for time-multiplexing optical pulse signals of a plurality of channels. For example, optical pulse signals for two channels are converted into optical pulses adjacent to the optical pulse train of one of the optical pulse signals. In this method, the optical pulse train of the other optical pulse signal is multiplexed so as to enter, and an optical time division multiplexed optical pulse signal in which the optical pulse signals of both channels are time-multiplexed is obtained.

  For example, if the optical pulse signal of the first channel with a bit rate of 40 Gb / s and the optical pulse signal of the second channel with the same bit rate of 40 Gb / s are multiplexed by bit interleaving, the bit rates of both channels It can be transmitted as an optical pulse signal with a bit rate of 80 Gb / s corresponding to the sum. The optical time-division multiplexed optical pulse signal transmitted in this way is separated as an optical pulse signal of each channel in the receiving device, and again the same as the optical pulse signal of the first channel with a bit rate of 40 Gb / s. The optical pulse signal of the second channel with a rate of 40 Gb / s is obtained, and the optical pulse signal of each channel is separated and reproduced.

  That is, the optical delay unit 76 inserts the optical pulse of the second channel optical pulse signal 75 between the adjacent optical pulses of the optical pulse train of the first channel optical pulse signal 73 (time slot). It plays a role of adding a delay corresponding to half the time of the time slots of the first and second channels to the optical pulse signal 75 of the second channel. The optical pulse signal 75 of the second channel passes through the optical delay device 76, is added with a time delay corresponding to half the time of the above-described time slot, and is output as the optical pulse signal 77 of the second channel. .

In the above-described example in which the optical pulse signals of the first and second channels having a bit rate of 40 Gb / s are bit-interleaved and time-division multiplexed, the time slot of the optical pulse signals of both channels (1 / (40 × 10 ⁹ )) A delay of 1.25 × 10 ⁻¹¹ s, which is half of s = 2.5 × 10 ⁻¹¹ s, is added to the optical pulse signal 75 of the second channel by the optical delay device 76. In this case, for example, a glass plate having a refractive index of 1.5 and a thickness of 2.5 cm can be realized as the optical delay device. That is, by inserting a glass plate having a refractive index of 1.5 and a thickness of 2.5 cm between the VOA 74 and the optical multiplexer 80, the optical pulse signal 75 of the second channel is bit-interleaved with the optical pulse signal 73 of the first channel. Thus, it is possible to generate two multiplexed optical time division multiplexed optical pulse signals 81.

  The optical pulse signal 73 of the first channel and the optical pulse signal 77 of the second channel are combined by the optical multiplexer 80, and output from the optical multiplexer 80 as a two-multiplexed optical time division multiplexed optical pulse signal 81. . Hereinafter, the two-time optical time-division multiplexed optical pulse signal may be simply referred to as an optical time-division multiplexed optical pulse signal or an optical pulse signal as long as no misunderstanding occurs.

  Here, a process of generating the first channel optical pulse signal 73 and the second channel optical pulse signal 75 will be described. First, the VOA 72 of the first channel has a low frequency that is the sum of the low frequency signal 115 within a range of several Hz to several MHz from the low frequency signal generator 110 and the DC bias voltage 113 from the DC voltage setting circuit 112. A modulation signal 119 is supplied. Here, an RF signal of 1.0 kHz was used as the low frequency signal 115. The low frequency signal 115 was set so that the low frequency modulation amplitude of the optical pulse signal in the VOA 72 was within the range of 0.5 to 1.0 dB.

  The VOA 74 of the second channel also has a low frequency modulation which is the sum of a low frequency signal 125 within the range of several Hz to several MHz from the low frequency signal generator 126 and a DC bias voltage 121 from the DC voltage setting circuit 120. A signal 123 is provided. However, the frequency of the low frequency signal 125 is such that the difference from the frequency of the low frequency signal 115 is greater than 1/100 of the frequency of the low frequency signal 115 so that it can be easily separated from the low frequency modulation signal 119 of the first channel. Set to. Further, the frequency of the low frequency signal 125 was set not to be equal to an integral multiple or a fraction of an integer of the frequency of the low frequency modulation signal 119. Here, the frequency of the low frequency signal 125 is set to 1.1 kHz. Also in the second channel, the low frequency signal 125 is set so that the low frequency modulation amplitude of the optical pulse signal in the VOA 74 falls within the range of 0.5 to 1.0 dB.

  The optical time division multiplexed optical pulse signal 81 is divided by the second optical demultiplexer 82 into an optical time division multiplexed optical pulse signal 83a and an optical time division multiplexed optical pulse signal 83b. One optical time division multiplexed optical pulse signal 83b becomes an optical time division multiplexed optical pulse signal to be transmitted, and the other optical time division multiplexed optical pulse signal 83a is used as a signal for detecting the peak value of the optical pulse. .

  The photoelectric converter 84 performs Step B2 of photoelectrically converting the optical time division multiplexed optical pulse signal 83a into an electrical pulse signal 85. The optical time division multiplexed optical pulse signal 83a is an optical pulse signal obtained by N-channel multiplexing of an optical pulse signal on which a low-frequency modulation signal is superimposed for each N channel in an N-channel optical time division multiplexing system.

  The first filter 86 receives the electric pulse signal 85, removes the high frequency component of the electric pulse signal 85, that is, the frequency component sufficiently higher than the frequency of the low frequency modulation signals 119 and 123, and the low frequency modulation signal 119 and the low frequency modulation. Step B3 of outputting the electric signal 87, which is synthesized with the signal 123, is executed. The first filter 86 can use LPF. Since there is a possibility that the electrical pulse signal 85 includes a frequency component lower than the low frequency modulation component 87, in this case, it is preferable to use a BPF that transmits only the low frequency modulation component 87.

  The electrical signal 87 is a low frequency modulation component having a frequency equal to the low frequency modulation signal output from the low frequency signal generators 110 and 126. The electric signal 87 is branched by the branching device 88 into an electric signal 87b and an electric signal 87a.

  First, the DC voltage signal extraction unit 174 for the first channel will be described. The DC voltage signal extraction unit 174 for the first channel includes a DC voltage setting circuit 112, a low frequency signal generator 110, a phase adjuster 114, a mixer 90, and a second filter 94.

  An electric signal 87 a having a frequency component equal to the frequency of the low frequency modulation signal 111 and a low frequency modulation signal 116 are input to the mixer 90. The low frequency modulation signal 116 is an RF modulation signal supplied from the low frequency signal generator 110 and is a signal whose phase is adjusted by the phase adjuster 114. The other input signal, electric signal 87a, is extracted from optical pulse signal 83a.

  Next, the DC voltage signal extraction unit 176 for the second channel will be described. The DC voltage signal extraction unit 176 for the second channel includes a DC voltage setting circuit 120, a low frequency signal generator 126, a phase adjuster 98, a mixer 92, and a second filter 96.

  Since the second filter 94 and the second filter 96 are responsible for extracting the DC voltage signal 95 and the DC voltage signal 97, respectively, it is preferable to use LPF and BPF cannot be used.

  An electric signal 87 b having a frequency component equal to the frequency of the low frequency modulation signal 127 and a low frequency modulation signal 99 are input to the mixer 92. The low frequency modulation signal 99 is an RF modulation signal supplied from the low frequency signal generator 126 and is a signal whose phase is adjusted by the phase adjuster 98. The other input signal, electric signal 87b, is extracted from optical pulse signal 83a.

  The first channel DC voltage signal extraction unit 174 and the second channel DC voltage signal extraction unit 176 of the optical pulse peak value control device are the same as the DC voltage signal extraction unit 178 and the second optical pulse of the first optical pulse peak value observation device. Corresponds to the two-phase lock-in amplifier 180 of the crest observation device. The case of using a two-phase lock-in amplifier will be described later.

  Here, with reference to FIGS. 6A to 6G, the operation principle of the optical pulse peak value control apparatus will be described. In FIGS. 6A to 6G, the horizontal axis scales time on an arbitrary scale, and the vertical axis scales light intensity on an arbitrary scale.

  As shown in FIG. 5, the optical pulse train 55 that has passed through the point P is divided into two by an optical demultiplexer 62 to become an optical pulse train 61 and an optical pulse train 63, and the optical modulator 64 and the second channel of the first channel, respectively. To the optical modulator 68. Since the first channel optical pulse signal 65 and the second channel optical pulse signal 69 output from the first channel optical modulator 64 and the second channel optical modulator 68, respectively, have the same phase, These can be shown as FIG. 6 (A) and FIG. 6 (B), respectively. Here, a case where optical pulses are present in all time slots is shown. Since it is actually an RZ-encoded optical pulse signal, there is a time slot in which no optical pulse exists.

  Here, assuming that the optical delay device 76 does not exist, at the positions of the point Q and the point R at the same position from the respective output ends of the VOA 72 and the VOA 74, the optical pulse signal 73 and the second signal of the first channel If the optical pulse signal 75 of the channel is observed, there is no phase shift between them. However, an optical delay unit 76 is inserted between the VOA 74 in the second channel transmission line and the optical multiplexer 80, and the optical delay signal 76 causes the optical pulse signal 75 of the second channel to be half of the time slot. A corresponding phase lag is added. Therefore, if the optical pulse signal 77 of the second channel is observed at the position of the point R, as shown by the broken line in FIG. 6 (C), the optical pulse signals shown in FIGS. 6 (A) and 6 (B) An optical pulse signal with a phase delay corresponding to half of the time slot is observed.

  The optical pulse signal 73 and the optical pulse signal 77 are output as a two-multiplexed optical time division multiplexed optical pulse signal 81 that is multiplexed by the optical multiplexer 80 and bit-interleaved. When the two-multiplexed optical time division multiplexed optical pulse signal 81 is observed at the point S, the waveform shown in FIG. 6 (D1) or FIG. 6 (D2) is observed.

  If the peak values of the optical pulse signal 73 and the optical pulse signal 77 are different, the waveform observed at the point S becomes the waveform shown in FIG. 6 (D1), and if the peak values of both are equal, the waveform shown in FIG. 6 (D2) is obtained. The waveform is as shown. The optical pulse peak value control device according to the second aspect of the present invention is such that the waveform observed as the double multiplexed optical time division multiplexed optical pulse signal 81 at the point S becomes the waveform shown in FIG. 6 (D2). The purpose of this is to make the peak values of both the pulse signal 73 and the optical pulse signal 77 equal.

  The waveforms shown in FIGS. 6E to 6G are drawn ignoring the half width of the optical pulse. Each line segment arranged vertically on the time axis (horizontal axis) represents one optical pulse. Therefore, the horizontal scale in FIGS. 6A to 6D2 is different from the horizontal scale in FIGS. 6E to 6G.

  The optical pulse signal 73 observed at the point Q is a curve connecting the peak values of the optical pulse (broken line connecting the upper end of the line segment indicating the optical pulse in FIG. 6E) is a low frequency signal generator. The waveform is equal to the frequency of the modulation signal (RF signal) 115 supplied from 110 and is a sine wave of 1.0 kHz. In addition, the optical pulse signal 77 observed at the point R is a curve connecting the peak values of the optical pulse (broken line connecting the upper end of the line segment indicating the optical pulse in FIG. 6F) is a low frequency signal. The waveform is equal to the frequency of the modulation signal (RF signal) 125 supplied from the generator 126, and is a sine wave of 1.1 kHz. In FIG. 6 (E) and FIG. 6 (F), in order to distinguish between the optical pulse constituting the optical pulse signal 73 and the optical pulse constituting the optical pulse signal 77, the former optical pulse is represented by a solid line with the latter optical pulse. Pulses are indicated by broken lines.

  If the peak values of both the optical pulse signal 73 and the optical pulse signal 77 are adjusted to be equal, the waveform observed at the point S is the waveform shown in FIG. 6 (D2) and FIG. 6 (G). Therefore, in the two-time optical time division multiplexed optical pulse signal 81, a low frequency modulation component having a frequency of 1.0 kHz and a low frequency modulation component having a frequency of 1.1 kHz are mixed and present.

  As described above, for the sake of simplicity, the description has been given by taking the optical time division multiplexed optical pulse signal 81 in the case of two multiplexing as an example. However, the above description is extended to N channels even for an N multiplexed optical time division multiplexed optical pulse signal. If it does, it will hold. In this case, the optical pulse signal corresponding to the two-time optical time-division-multiplexed optical pulse signal 81 has a mixture of low-frequency modulation components different from integer multiples or fractions of one of N frequencies. is doing.

  Therefore, the photoelectric converter executes a step of photoelectrically converting the optical pulse signal for each N channel on which the low-frequency modulation signal is superimposed into an electric pulse signal.

  The optical pulse signal 83a is an optical pulse signal obtained by dividing the double multiplexed optical time division multiplexed optical pulse signal 81 into two. Therefore, the optical pulse signal shown in FIG. 6 (G) is the same as the optical pulse signal except that the intensity thereof is relatively weak. When the electric pulse signal 85 obtained by photoelectrically converting the optical pulse signal 83a is filtered by the first filter 86, the frequency (several tens of GHz) component of the clock signal of the optical pulse signal is removed, and the electric signal 87 is obtained. . The electric signal 87 is an electric signal including only low frequency modulation components of 1.0 kHz and 1.1 kHz.

  The electric signals 87a and 87b branched from the electric signal 87 by the branching device 88 are input to the mixer 90 and the mixer 92, respectively.

  In the mixer 90, the electric signal 87a and the low frequency modulation signal 116 are input, and the mixing signal 91 is output. The mixing signal 91 is the first when the phase of the low frequency modulation component equal to the frequency of the modulation signal 115 in the low frequency modulation component included in the electrical signal 87a matches the phase of the low frequency modulation signal 116. It becomes a DC voltage signal proportional to the peak value of the optical pulse of the channel.

  Further, in the mixer 92, the electric signal 87b and the low frequency modulation signal 99 are input and a mixing signal 93 is output. The mixing signal 93 is the second when the phase of the low frequency modulation component whose frequency is equal to the frequency of the modulation signal 125 and the phase of the low frequency modulation signal 99 of the low frequency modulation components included in the electrical signal 87b match. It becomes a DC voltage signal proportional to the peak value of the optical pulse of the channel.

  By passing the mixing signal 91 and the mixing signal 93 through the second filter 94 and the second filter 96 that transmit only the DC component and remove the other frequency components, respectively, the optical pulses of the first channel and the second channel are transmitted. It can be observed as a DC voltage signal 95 and a DC voltage signal 97 that are proportional to the peak values of the optical pulses constituting the signal. As the second filter 94 and the second filter 96, it is desirable to use a filter that attenuates the transmitted electric signal by 30 dB or more at least at 50 Hz.

  From the above description, the mixer 90 and the mixer 92 are the electric signals 87a and 87b having the same frequency components as the low frequency modulation signals 115 and 125 extracted from the electric pulse signal 83a, respectively, and the low frequency modulation signals 116 and 99. Step B4 is generated to generate mixing signals 91 and 93. In the N channel optical time division multiplexing system, a mixer is provided for each N channel. In addition, a second filter 94 and a second filter 96 are also provided for each N channel. From each second filter, a wave for each channel is obtained as a DC voltage signal proportional to the peak value of the optical pulse constituting each optical pulse signal. Convert to high value and output.

  That is, the mixer performs Step B4 of mixing the low frequency modulation component and the low frequency modulation signal to generate a mixing signal for each N channel. In addition, the second filter executes step B5 for removing high frequency components from the mixing signal and converting it into a DC voltage signal for each N channel proportional to the peak value of the optical pulse constituting the optical pulse signal.

  A method and apparatus for realizing the above steps B4 and B5 by the two-phase lock-in amplifier unit 180 of the second optical pulse peak value observation apparatus described in the first embodiment will be described. The two-phase lock-in amplifier unit 180 of the second optical pulse peak value observation device shown in FIG. 3 is connected to the first channel DC voltage signal extraction unit 174 and the second channel DC signal of the optical pulse peak value control device shown in FIG. This may be applied to the voltage signal extraction unit 176.

  At this time, the correspondence between the two-phase lock-in amplifier unit 180 and the DC voltage signal extraction unit 174 of the first channel is as follows. The DC voltage setting circuit 22 and the low frequency signal generator 24 of the two-phase lock-in amplifier unit 180 correspond to the DC voltage setting circuit 112 and the low frequency signal generator 110 of the DC voltage signal extraction unit 174 of the first channel, respectively. . Further, the DC voltage signal 147 that is an output signal from the two-phase lock-in amplifier unit 180 corresponds to the DC voltage signal 95 that is an output signal from the DC voltage signal extraction unit 174 of the first channel. The portion composed of the first mixer 54, the second mixer 56, and the 90 ° phase delay unit 58 of the two-phase lock-in amplifier unit 180 includes the phase modulator 144 and the mixer 90 of the DC voltage signal extraction unit 174 of the first channel. Corresponds to the part composed of

  Further, the DC voltage setting circuit 22 and the low frequency signal generator 24 of the two-phase lock-in amplifier unit 180, and the DC voltage setting circuit 120 and the low frequency signal generator 126 of the second channel DC voltage signal extraction unit 176, respectively. Correspond. Further, the DC voltage signal 147 that is an output signal from the two-phase lock-in amplifier unit 180 corresponds to the DC voltage signal 97 that is an output signal from the DC voltage signal extraction unit 176 of the second channel. The portion composed of the first mixer 54, the second mixer 56, and the 90 ° phase delay unit 58 of the two-phase lock-in amplifier unit 180 includes the phase modulator 98 and the mixer 92 of the DC voltage signal extraction unit 176 of the second channel. Corresponds to the part composed of

  When the above-described Step B4 and Step B5 are realized by the two-phase lock-in amplifier unit 180 of the second optical pulse peak value observation apparatus described in the first embodiment, it is as follows. Note that these Step B4 and Step B5 are steps corresponding to Step B4 and Step B5 in the optical pulse peak value observation method according to the first invention. In the following description, a general N-channel optical time division multiplexing apparatus is assumed. In view of the above description, if the description is generalized to the N-channel optical time division multiplexing apparatus as described below, the above-described steps B4 and B5 are the same as those described in the first embodiment. The contents of the invention regarding the method and apparatus realized by the two-phase lock-in amplifier unit 180 of the optical pulse peak value observation apparatus will be apparent to those skilled in the art.

  Step B4 is a step B4-1: a step of bifurcating a low frequency modulation component for each N channel into a first low frequency modulation component and a second low frequency modulation component; and step B4-2: first low frequency Mixing the frequency modulation component and the low frequency modulation signal every N channels to generate a first mixing signal for each N channel; and step B4-3: delaying the phase of the low frequency modulation signal by 90 ° for each N channel Generating a 90 ° delayed low frequency modulation signal and mixing a second low frequency modulation component for each N channel and a 90 ° delayed low frequency modulation signal to generate a second mixing signal for each N channel. Consists of.

  Step B4-1 is executed by branching into two by N branching units installed for each N channel and branching into a first low frequency modulation component and a second low frequency modulation component for each N channel.

  The first low frequency modulation component and the low frequency modulation signal are divided into the first low frequency modulation component and the second low frequency modulation component. Step B4-2 is performed to generate a first mixing signal for each N channel.

  The N second mixers installed for each N channel mix the second low-frequency modulation component and the delayed low-frequency modulation signal delayed by 90 ° with respect to the phase of the low-frequency modulation signal for each N channel. Step B4-3 for generating the second mixing signal is executed.

  Step B5 is a step B5-1: removing each high-frequency component from the first mixing signal and the second mixing signal, and for each N channel proportional to the peak value of the optical pulse constituting the optical pulse signal for each N channel. A step of converting the first voltage value and the second voltage value into a step B5-2: generating a root mean square value of the first voltage value and the second voltage value as a DC voltage signal for each N channel It is comprised including.

  N second filters and third filters installed for each N channel remove high-frequency components from the first mixing signal and the second mixing signal, respectively, and generate optical pulse signals constituting the optical pulse signal for each N channel. Step B5-1 is executed to convert each of the first voltage value and the second voltage value for each N channel proportional to the peak value.

  The N mean square value generators installed for each N channel generate a DC voltage signal that is a mean square value of the first voltage value and the second voltage value for each N channel for each N channel. Perform B5-2.

  The peak value data generation unit will be described with reference to FIG. The peak value data generation unit is the same as that of the first and second optical pulse peak value observation apparatuses in the first embodiment described above. Therefore, the peak value data generation step is also referred to as “step C” in the optical pulse peak value control apparatus according to the second embodiment.

  Step C includes steps C1 to C3 shown below.

That is, step C1: setting a reference voltage value, step C2: collecting a DC voltage signal proportional to the peak value of the optical pulse constituting the optical pulse signal for each N channel for each N channel, and step C3 A step of generating a voltage value for each N channel corresponding to a difference between the collected DC voltage signal for each N channel and a reference voltage value as peak value data.

  In the following description, the case of two channels will be described as an example. That is, the case of N = 2 will be described, but the same applies to the case of N = 3 or more.

  FIG. 7 is a schematic block configuration diagram of the peak value data generation unit 130 of the optical pulse peak value control apparatus.

The peak value data generation unit 130 for realizing the peak value data generation step (step C) includes an initial value data storage unit 150, a data collection unit 154, and a data processing unit 160. In addition, a control unit 158 for controlling the initial value data storage unit 150, the data collection unit 154, and the data processing unit 160 is provided. The peak value data generation unit 130 outputs a voltage value corresponding to the difference between the reference voltage value and the DC voltage signals 95 and 97 output from the peak value detection unit 100 as the peak value data 131.

  In FIG. 7, only one output line for outputting the peak value data 131 is drawn. However, from the output line for outputting the peak value data 131, the reference voltage value and the peak value detection unit 100 are set for each channel. A voltage value corresponding to the difference from the output DC voltage signal is output for each channel at intervals.

The initial value data storage unit 150 executes step C1 for storing a reference voltage value set as a voltage value corresponding to the reference peak value. Data collection unit 154 is detected by the peak value detection step, collecting a DC voltage signal proportional to the peak value of the optical pulses constituting the optical pulse signal of each channel, it executes Step C2. The data processing unit 160 executes Step C3 in which a voltage value corresponding to the difference between the DC voltage signal collected in Step C2 and the reference voltage value is generated as peak value data.

  First, the DC voltage signal 95 related to the first channel output from the second filter 94 and the DC voltage signal 97 related to the second channel output from the second filter 96 are shown in FIG. The output terminal of the second filter 96 is connected so as to be input to the initial value data storage unit 150.

  Then, in the initial value data storage unit 150, the second filter 94 or the second filter 96 stores the peak value of the optical pulse constituting the optical pulse signal 81 obtained in advance by a waveform monitor or the like in a desired value. The voltage value (initial voltage value) of the output DC voltage signal is stored. The goal is to adjust the initial voltage value so that the peak values of the optical pulses of all channels match.

Next, the output terminals of the second filter 94 and the second filter 96 are connected to the data collector so that the DC voltage signals 95 and 97 output from the second filter 94 and the second filter 96 are input to the data collector 154. Reconnect to 154 input terminals. After this, the DC voltage signals 95 and 97 output from the second filter 94 and the second filter 96 are sequentially sent to the data processing unit 160 as DC voltage signals 155 and 157. The data processing unit 160 compares the values of the DC voltage signals 95 and 97 output from the second filter 94 and the second filter 96 with the initial voltage value 151 output from the initial value data storage unit 150, and compares the magnitudes thereof. If the value is large, a positive value is output. If the value is small, a negative value is output. That is, the data processing unit 160 outputs the difference between the DC voltage signals 95 and 97 and the initial voltage value 151 supplied from the initial value data storage unit 150 for each channel.

The control unit 158 instructs the execution of step C1 to store the reference voltage value set as the voltage value corresponding to the reference peak value in the initial value data storage unit 150. Further, the data collection unit 154 is controlled to instruct the execution of step C2 to collect a direct-current voltage signal that is detected in the peak value detection step and is proportional to the peak value of the optical pulse constituting the optical pulse signal 81. In addition, the data processing unit 160 is controlled to instruct the execution of step C3 to generate a voltage value corresponding to the difference between the DC voltage signal collected in step C2 and the reference voltage value as peak value data.

  If the values of the DC voltage signals 95 and 97 output from the second filter 94 and the second filter 96 are larger than the initial voltage value, it means that the peak value of the optical pulse corresponding to the voltage value set as the initial voltage value is large. To do. Conversely, if it is smaller than the initial voltage value, it means that the peak value of the optical pulse corresponding to the voltage value set as the initial voltage value is small. Therefore, the peak value data generated in step C3 is a signal indicating whether the peak value of the optical pulse constituting the optical pulse signal 81 is smaller or larger than the reference peak value. From this peak value data, it is possible to know how much the peak value of the optical pulse constituting the optical pulse signal 81 is deviated from the reference peak value with respect to the reference peak value.

  The example described above is for the case of 2 channels, but the same applies to the case of 3 channels or more. When the DC voltage signal output from the second filter is 2 channels, there are 2 types (DC voltage signals 95 and 97) equal to the number of channels, but when there are 3 channels or more, for example, when the channel is N channel Will be N types. N types of voltage values corresponding to the difference between the N types of DC voltage signals output from the N types of second filters and the reference voltage value are output as peak value data. In FIG. 7, these N types of peak value data output from the data processing unit 160 are depicted as peak value data 131 as a representative line.

  The functions of the peak value data generation unit described above are summarized as follows. That is, the peak value data generation unit generates a voltage value for each N channel corresponding to the difference between the reference voltage value set as the voltage value corresponding to the reference peak value and the DC voltage signal detected in the peak value detection step. A peak value data generation step for generating as high value data is executed.

  Next, the function of the bias voltage control unit will be described. The bias voltage control unit has a peak value control step for controlling the peak value of the optical pulse for each of the N channels constituting the optical pulse signal so that the peak value data for each of the N channels are equal to each other. The part to execute.

  First, a method for manually performing the peak value control step will be described. As a method for automating, in a third embodiment, which will be described later, a method of realizing the crest value data generation step and the crest value control step by computer control is presented.

Desired value as the peak value of the optical pulses constituting the optical pulse signal to be transmitted, determines et is Ru as a design value of the optical time division multiplex transmission system. It is important for the operation of the optical time division multiplex transmission system to always keep the peak values of the optical pulses constituting the optical pulse signals of all the channels to be time division multiplexed at this desirable peak value.

Therefore, the peak value data 131 of each channel output from the peak value data generation unit is read, compared with the above-described desirable peak value, and the DC bias voltage component supplied to the VOA 72 or 74 shown in FIG. Adjust. The DC bias voltage component supplied to the variable optical attenuator 72 or 74 can be increased or decreased by adjusting the DC voltage setting circuit 112 or 120, respectively. By doing so, the maximum peak values in FIGS. 6 (E) and 6 (F) corresponding to the maximum peak value I of the optical pulse signal shown in FIG. 2 (C) can be increased or decreased. 6 (E) and 6 (F) schematically show low-frequency superimposed optical pulse signals 73 and 77, respectively. The modulation intensity (the magnitude of the modulation component) received by the respective optical pulse signals 65 and 69 by the low-frequency modulation signals 119 and 123 is expressed as I _p-1 and I _p-2 , respectively. That is, the modulation amplitudes of the optical pulse signals shown as I _p-1 and I _p-2 in FIGS. 6E and 6F are the amplitudes I _{p of} the optical pulse signal shown in FIG. Corresponding to

If the low-frequency signal is not supplied from the low-frequency signal generator 110 or 126, the peak value of the optical pulse signal shown in FIGS . 6 (E) and 6 (F) is constant over time. . The peak values I _1-0 and I _2-0 of the optical pulse signal shown in FIG. 6 (D1) depend on the DC bias voltage components supplied to the variable optical attenuators 72 and 74, respectively. This DC bias voltage component is supplied from the DC voltage setting circuits 112 and 120 to the variable optical attenuators 72 and 74, respectively. Like the optical pulse signal shown in FIG. 6 (D1), even if the peak values I _1-0 and I _2-0 are different from each other, the DC bias voltage component supplied to the variable optical attenuators 72 and 74 is By adjusting the setting voltages of the DC voltage setting circuits 112 and 120, respectively, the peak values I _{1-0 ′} and I _{2-0 ′} are made equal to each other as in the optical pulse signal shown in FIG. 6 (D2). Can do. That is, it means that the peak value of the optical pulse signal can be adjusted by adjusting the DC bias voltage component supplied to the variable optical attenuator.

  When the bias voltage control unit manually performs the peak value control step, the optical pulse peak value adjustment operator reads the peak value data 131 of each channel output from the peak value data generation unit, and The function can be replaced by adjusting the peak value of each channel by adjusting the DC voltage setting circuit. That is, the operator adjusting the optical pulse peak value controls the peak value of the optical pulse for each N channel constituting the optical pulse signal so that the peak value data for each N channel are all equal to each other. Can do.

  In a third embodiment to be described later, a method for realizing the function performed by the above-described optical pulse peak value adjusting operator by computer control is presented.

<Third embodiment>
With reference to FIG. 8, a method for automating the control of the crest value of an optical pulse will be described in which a crest value data generation step and a crest value control step are integrated and realized by computer control.

FIG. 8 is a schematic block diagram of an optical pulse peak value automatic control unit. The peak value automatic control unit 200 includes a peak value data generation unit 199 and a bias voltage control unit 196. The peak value data generation unit 199 includes a data input unit 186, an initial value data storage unit 188, a data collection unit 192, and a data processing unit 194. The data input unit 186, the initial value data storage unit 188, the data collection unit 192, and the control unit 190 for controlling the data processing unit 194 are provided.

  The following description will be made on the assumption that the first optical pulse peak value observation apparatus of the first embodiment is used. Of course, the method for automating the control of the crest value of the optical pulse presented in the third embodiment is the same as the second optical pulse crest observation device of the first embodiment or the light of the second embodiment. The same can be done when using a pulse peak value control device.

  The optical pulse peak value automatic control method according to the third embodiment includes first to ninth steps described below. With reference to FIG. 8 and FIG. 9, a method for automatically controlling the crest value of an optical pulse will be described. FIG. 9 is a flowchart of an optical pulse peak value automatic control method. In the following description, the first to ninth steps will be referred to as steps S1 to S9, respectively, so that the correspondence with the symbols in the flowchart shown in FIG. 9 is easy to see. In the flowchart shown in FIG. 9, the boxed portion S1 indicates the contents corresponding to the first step. Similarly, the contents corresponding to the second step to the ninth step are also shown for the enclosed portions indicated as S2 to S9.

  Step S1 is a step of setting a temporary voltage value in a DC voltage setting circuit that supplies a DC bias voltage to a variable optical attenuator that superimposes a low frequency modulation signal on an optical pulse signal. There are a plurality of elements that can be used as the variable optical attenuator, such as those using the thermo-optic effect and mechanical types in which a shielding plate is inserted in the optical path. Here, explanation will be made assuming that EAM is used.

  The relationship between the amount of optical loss of the EAM used as a variable optical attenuator and the bias voltage is different for each EAM. For this reason, in order to determine the bias voltage at which a desired amount of optical loss can be obtained, first, a temporary voltage value is set in the DC voltage setting circuit, and the optical pulse output from the variable optical attenuator for this temporary voltage value. It is necessary to grasp the relationship between the peak values of signals. Step S1 is a step for setting a temporary voltage value in the DC voltage setting circuit for this purpose.

  Step S2 observes the peak value of the optical pulse signal by the waveform monitor and determines whether or not this observed value is within the design value range. If this peak value is not within the design value range, the above step is performed. Returning to S1, if the crest value is within the design value range, this is a step of giving an instruction to the DC voltage setting circuit to set the temporary voltage value as the initial voltage value. This step determines a DC bias voltage to be supplied to the variable optical attenuator so that an optical pulse signal having a desired peak value is output from the variable optical attenuator.

  Steps S1 and S2 are steps that do not need to be executed once the variable optical attenuator is mounted on the optical time division multiplexing device unless the operational characteristics of the optical attenuator change over time. . Therefore, it is sufficient that step S1 and step S2 can be performed manually.

  In step S1 and step S2 described above, if it is confirmed that the peak value of the optical pulse signal observed by the waveform monitor is within the range of the design value, the DC voltage value supplied to the DC voltage setting circuit at that time is changed. The initial voltage value is set in the DC voltage setting circuit (step S3).

  When the initial voltage value is set in the DC voltage setting circuit, the DC voltage signal 183 corresponding to the optical pulse signal obtained as the output signal from the second filter 182 is input to the voltage output unit 184. Here, the second filter 182 corresponds to the second filter 32 shown in FIG. Further, the DC voltage signal 183 corresponds to the DC voltage signal 33 output from the second filter 32 shown in FIG. 1 or the DC voltage signal 147 output from the root mean square generation unit 146 shown in FIG.

  An analog signal / digital signal converter (A / D converter) can be used for the voltage output unit 184. The DC voltage signal 183 is converted from an analog signal to a digital signal by the voltage output unit 184. Thus, steps S4 to S9 described below can be realized by computer control.

  After the end of step S3, the digital DC voltage signal 185 that is the output data of the first voltage output unit 184 is input to the initial value data storage unit 188 (step S4). Thus, the reference voltage value is stored in the initial value data storage unit as a voltage value corresponding to the reference peak value.

  When the above steps S1 to S4 are completed, the initial setting of the optical time division multiplexing apparatus is completed. The subsequent steps are controlled so that the peak value of the optical pulse signal of a specific channel fluctuates for some reason while the optical time division multiplexing device is operating, so that the peak value is always kept within the design value range. It is a step to do. In the flowchart shown in FIG. 9, steps for controlling the peak value while the optical time division multiplexing apparatus is in operation are shown as step S3 ′ and steps S5 to S9.

While the optical time division multiplexing apparatus is in operation, an instruction is issued from the control unit 190 so that the output data 185 of the voltage output unit 184 is always input to the data collection unit 192 at a certain time interval (step S5). That is, steps S1 to S4 are completed, and after the initial setting of the optical time division multiplexing apparatus is completed, the step of inputting the second and subsequent output data of the voltage output unit to the data collection unit is step S5. Therefore, when the process proceeds to step S5 for the first time after the initialization of the optical time division multiplexing apparatus is completed, step S3 ′ is skipped. Then, the process proceeds to step S6 and step S7, and after step S8 or step S9, the process proceeds to step S3 ′.

The output data 185 of the voltage output unit 184 is periodically input from the data input unit 186 to the data collection unit 192 based on an instruction from the control unit 190. The difference between the reference voltage value, which is the voltage value corresponding to the reference peak value input to the initial value data storage unit 188 in step S4 described above, and the voltage value periodically input to the data collection unit 192 is the data Calculation is performed in the processing unit 194 (step S6). That is, step S6 calculates the difference between the output data of the voltage output unit input to the data collection unit and the output data of the voltage output unit input to the initial value data storage unit as the peak value data 195, and the data processing unit This is a step of outputting from 194. The reference voltage value input to the initial value data storage unit 188 and the voltage value periodically input to the data collection unit 192 are based on an instruction from the control unit 190, respectively, and the initial value data storage unit 188 and the data collection unit 192 to the data processing unit 194.

  The peak value data 195 output from the data processing unit 194 is input to the bias voltage control unit 196 to determine whether the value is a positive value or a negative value (step S7). Step S7 is executed in the bias voltage control unit 196, and its content is to determine whether the peak value data is positive or negative.

In the bias voltage control unit 196, the next step S8 or step S9 is executed. That is, if the peak value data is a negative value, the step of changing the initial voltage value set in the DC voltage setting circuit so as to reduce the optical loss amount of the variable optical attenuator (step S8), and the wave If the high-value data is a positive value , this is a step of changing the initial voltage value set in the DC voltage setting circuit so that the optical loss amount of the variable optical attenuator increases (step S9).

  As described above, the initial voltage value is set in the DC voltage value setting circuit in step S3. In step S8 or step S9, the initial value is changed and a new DC voltage value is reset in the DC voltage value setting circuit. Therefore, in the flowchart shown in FIG. 9, this resetting step is shown as step S3 ′. That is, as described above, after step S8 or step S9 is completed, the process does not return to the steps before step S4 (steps S1 to S4). After proceeding from step S1 to step S4 and then sequentially proceeding to step S5, step S6 and step S7, the process proceeds to step S8 or step S9 and then proceeds to step S3 ′.

  That is, when the program shown in FIG. 9 is started and step S4 is first completed, the initial voltage value is set in the DC voltage value setting circuit, so the voltage of the DC voltage value setting circuit must be changed. If not, go directly to step S5. At this time, step S3 ′ is skipped and the process proceeds from step S4 to step S5. However, after step S8 or step S9, the set voltage value of the DC voltage value setting circuit is changed from the initial voltage value to a new DC voltage value, and the process returns to step S3 ′.

  The bias voltage control unit 196 outputs a control signal 197 corresponding to the magnitude of the peak value data and the magnitude of the absolute value data, and the DC bias voltage value of the DC voltage control circuit 198 is set by the control signal 197.

  In the above description, the control content by the control unit 190 has been described where necessary. However, in addition to this, the control unit 190 displays the control status regarding the above-described steps S3 to S9 on a display device (not shown). .)), It is possible to provide a control function for outputting information on steps S3 to S9.

  As described above, according to the crest value automatic control method of the optical pulse, it is determined whether the crest value data is positive or negative, and the crest value data is automatically set to be always equal to 0. The DC bias component of the low frequency modulation signal supplied to the variable optical attenuator is controlled. Of course, for the convenience of system design, the peak value data is set to a constant value other than 0, and the low frequency is automatically supplied to the variable optical attenuator so that the peak value data is always equal to this constant value. It is also possible to take a method of controlling the DC bias component of the modulation signal.

  If the above-described peak value automatic control unit 200 is installed for each multiplexed channel, the peak value of the optical pulse constituting the optical pulse signal of each channel is automatically set to be always equal to the peak value corresponding to the initial data. Therefore, it is possible to automatically control the crest values of the optical pulses constituting the optical signals of the multiplexed channels to be always equal to each other.

  In the description so far, the voltage value corresponding to the difference between the reference voltage value set as the voltage value corresponding to the reference peak value and the DC voltage signal detected in the peak value detection step is used as the peak value data. . However, it is also possible to treat as peak value data not by the difference between the two but by the ratio between the two. Whether the difference between the two or the ratio is adopted as the peak value data belongs to the design matter.

FIG. 2 is a schematic block configuration diagram of a first optical pulse peak value observation apparatus. It is a figure where it uses for description of operation | movement of an optical modulator and a variable optical attenuator. FIG. 3 is a schematic block configuration diagram of a second optical pulse peak value observation apparatus. It is a schematic block diagram of a tandem type optical modulator. It is a schematic block diagram of an optical pulse peak value control device. It is a figure where it uses for description of the operation principle of an optical pulse peak value control apparatus. It is a schematic block block diagram of the peak value data generation part of an optical pulse peak value control apparatus. It is a schematic block block diagram of the crest value automatic control part of an optical pulse. It is a flowchart of the crest value automatic control method of an optical pulse.

Explanation of symbols

8, 66, 70: Modulated electrical signal generator
10, 64, 68: Optical modulator
12, 72, 74, 222: Variable Optical Attenuator (VOA)
14, 82: Optical splitter
16, 84: Photoelectric converter
18, 86: 1st filter
20, 90, 92: Mixer
22, 112, 120, 198: DC voltage setting circuit
24, 110, 126: Low frequency signal generator
26: Merger
28, 52, 88, 140: turnout
30, 98, 114: Phase adjuster
32, 94, 96, 182: Second filter
36, 154, 192: Data collection unit
38, 160, 194: Data processing section
42, 150, 188: Initial value data storage
44, 158, 190: Control unit
46, 130, 199: Peak value data generator
48, 100, 148: Peak value detector
50, 60: Optical pulse signal generator
51: Optical pulse signal generation modulator
54: First mixer
56: Second mixer
58: 90 ° phase delay
62: 1st optical demultiplexer
76: Optical delay device
80: Optical multiplexer
82: 2nd optical demultiplexer
134, 196: Bias voltage controller
142: Third filter
144: Fourth filter
146: root mean square value generator
161: First channel optical pulse signal generator
163: Second channel optical pulse signal generator
170: 1st channel optical pulse signal generation modulator
172: Second channel optical pulse signal generation modulation unit
174: DC voltage signal extractor for the first channel
176: DC voltage signal extractor for the second channel
178: DC voltage signal extractor
180: 2-phase lock-in amplifier
184: Voltage output section
186: Data input section
200: Crest value automatic control section
204: Condenser
206: Modulated electrical signal supply unit
208: Coil
210: Bias power supply
212a, 212b: P-side electrode
214: N side electrode
226, 228: Antireflection film
230: 1st light absorption area
232: Second light absorption region
234: Waveguide region
236: Optical waveguide
240: Tandem light modulator

Claims (13)

A crest value observation method of the optical pulses constituting the optical time division multiplex signal used time division multi Shigemichi the signal light by the synchronous detection,
An optical pulse signal generation step of generating an optical pulse signal by modulating an optical pulse train having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal with a modulation signal synchronized with the clock signal;
A peak value detecting step of detecting a peak value of an optical pulse constituting the optical pulse signal by converting it to a DC voltage signal proportional to the peak value of the optical pulse;
Peak value data generation step for generating, as peak value data, a voltage value corresponding to the difference between the reference voltage value set as the same value for all channels as the voltage value corresponding to the reference peak value and the DC voltage signal And
The peak value detecting step includes
Superposing a low frequency modulation signal corresponding to the sum of a DC bias voltage and a modulation signal having a frequency lower than the frequency of the clock signal on the optical pulse signal to generate a low frequency superimposed optical pulse signal;
Photoelectrically converting the low-frequency superimposed optical pulse signal into an electrical pulse signal;
Extracting a low frequency modulation component that is a frequency component equal to the low frequency modulation signal from the electrical pulse signal;
Mixing the low frequency modulation component and the low frequency modulation signal to generate a mixing signal;
An optical pulse peak value observing method comprising: removing a high frequency component from the mixing signal and converting the mixed signal into a DC voltage signal proportional to a peak value of an optical pulse constituting the optical pulse signal. A crest value observation method of the optical pulses constituting the optical time division multiplex signal used time division multi Shigemichi the signal light by the synchronous detection,
An optical pulse signal generation step of generating an optical pulse signal by modulating an optical pulse train having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal with a modulation signal synchronized with the clock signal;
A peak value detecting step of detecting a peak value of an optical pulse constituting the optical pulse signal by converting it to a DC voltage signal proportional to the peak value of the optical pulse;
Peak value data generation step for generating, as peak value data, a voltage value corresponding to the difference between the reference voltage value set as the same value for all channels as the voltage value corresponding to the reference peak value and the DC voltage signal And
The peak value detecting step includes
Superposing a low frequency modulation signal corresponding to the sum of a DC bias voltage and a modulation signal having a frequency lower than the frequency of the clock signal on the optical pulse signal to generate a low frequency superimposed optical pulse signal;
Photoelectrically converting the low-frequency superimposed optical pulse signal into an electrical pulse signal;
Extracting a low frequency modulation component that is a frequency component equal to the low frequency modulation signal from the electrical pulse signal;
Bifurcating the low frequency modulation component into a first low frequency modulation component and a second low frequency modulation component;
Mixing the first low frequency modulation component and the low frequency modulation signal to generate a first mixing signal;
The phase of the low frequency modulation signal is delayed by 90 ° to generate a 90 ° delayed low frequency modulation signal, and the second low frequency modulation component and the 90 ° delayed low frequency modulation signal are mixed to generate a second mixing signal. Generating step;
A step of removing high frequency components from the first mixing signal and the second mixing signal, respectively, and converting each of the first voltage value and the second voltage value proportional to the peak value of the optical pulse constituting the optical pulse signal. When,
An optical pulse peak value observation method comprising: generating a DC voltage signal that is a mean square value of the first voltage value and the second voltage value. In the optical pulse peak value observation method according to claim 1 or 2,
The peak value data generation step includes
Setting the reference voltage value;
Collecting a DC voltage signal proportional to the peak value of the optical pulse constituting the optical pulse signal;
And generating a voltage value corresponding to a difference between the collected DC voltage signal and the reference voltage value as peak value data. A peak value observation apparatus of the optical pulses constituting the optical time division multiplex signal used time division multi Shigemichi the signal light by the synchronous detection,
An optical pulse signal generation unit that generates an optical pulse signal by modulating an optical pulse train that has a repetition frequency equal to the frequency of the clock signal and is synchronized with the clock signal with a modulation signal that is synchronized with the clock signal;
A peak value detection unit that detects a peak value of an optical pulse constituting the optical pulse signal by converting it to a DC voltage signal proportional to the peak value of the optical pulse;
Crest value data generation that generates a voltage value corresponding to the difference between the reference voltage value set as the same value for all channels as the voltage value corresponding to the reference peak value and the DC voltage signal as peak value data With parts,
The peak value detector is
A variable optical attenuator that generates a low-frequency superimposed optical pulse signal by superimposing a low-frequency modulated signal corresponding to the sum of a DC bias voltage and a modulated signal having a frequency lower than the frequency of the clock signal on the optical pulse signal;
A photoelectric converter that photoelectrically converts the low-frequency superimposed optical pulse signal into an electrical pulse signal; and
A first filter that extracts a low frequency modulation component that is a frequency component equal to the low frequency modulation signal from the electrical pulse signal;
A mixer that mixes the low frequency modulation component and the low frequency modulation signal to generate a mixing signal;
An optical pulse peak value observation device comprising: a second filter that removes a high frequency component from the mixing signal and converts it to a direct current voltage signal proportional to the peak value of the optical pulse constituting the optical pulse signal. . A peak value observation apparatus of the optical pulses constituting the optical time division multiplex signal used time division multi Shigemichi the signal light by the synchronous detection,
An optical pulse signal generation unit that generates an optical pulse signal by modulating an optical pulse train that has a repetition frequency equal to the frequency of the clock signal and is synchronized with the clock signal with a modulation signal that is synchronized with the clock signal;
A peak value detection unit that detects a peak value of an optical pulse constituting the optical pulse signal by converting it to a DC voltage signal proportional to the peak value of the optical pulse;
Crest value data generation that generates a voltage value corresponding to the difference between the reference voltage value set as the same value for all channels as the voltage value corresponding to the reference peak value and the DC voltage signal as peak value data With parts,
The peak value detector is
A variable optical attenuator that generates a low-frequency superimposed optical pulse signal by superimposing a low-frequency modulated signal corresponding to the sum of a DC bias voltage and a modulated signal having a frequency lower than the frequency of the clock signal on the optical pulse signal;
A photoelectric converter that photoelectrically converts the low-frequency superimposed optical pulse signal into an electrical pulse signal; and
A first filter that extracts a low frequency modulation component that is a frequency component equal to the low frequency modulation signal from the electrical pulse signal;
A branching device bifurcating the low frequency modulation component into a first low frequency modulation component and a second low frequency modulation component;
A first mixer that mixes the first low frequency modulation component and the low frequency modulation signal to generate a first mixing signal;
A second mixer that generates a second mixing signal by mixing the second low-frequency modulation component and a delayed low-frequency modulation signal delayed by 90 ° with respect to the phase of the low-frequency modulation signal;
A high-frequency component is removed from each of the first mixing signal and the second mixing signal, and converted into a first voltage value and a second voltage value that are proportional to the peak value of the optical pulse constituting the optical pulse signal, respectively. 2 filters and a third filter;
An optical pulse peak value observing device comprising: a mean square value generator that generates a mean square value of the first voltage value and the second voltage value as a DC voltage signal. In the optical pulse peak observation device according to claim 4 or 5,
The peak value data generation unit
An initial value data storage unit for storing the reference voltage value set as a voltage value corresponding to a reference peak value;
A data collection unit for collecting a DC voltage signal proportional to the peak value of the optical pulse constituting the optical pulse signal;
An optical pulse peak value observation apparatus comprising: a data processing unit that generates a voltage value corresponding to a difference between the collected DC voltage signal and the reference voltage value as peak value data. A peak value control method of the optical pulses constituting the optical time division multiplex signal used time division multi Shigemichi the signal light by the synchronous detection,
An optical pulse train having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal is modulated with a modulation signal synchronized with the clock signal to generate an optical pulse signal for each N channel (N is a natural number of 2 or more). An optical pulse signal generation step to generate;
For every N channels,
A peak value detecting step of detecting a peak value of an optical pulse constituting the optical pulse signal by converting it to a DC voltage signal proportional to the peak value of the optical pulse;
For every N channels,
As a voltage value corresponding to the reference peak value, a voltage value corresponding to the difference between the reference voltage value set as the same value for all channels and the DC voltage signal detected in the peak value detection step is Crest value data generation step to generate as high value data;
For every N channels,
A crest value control step for controlling crest values of the optical pulses constituting the optical pulse signal so that the crest value data are all equal to each other,
The peak value detecting step includes
For every N channels,
A step of generating a low frequency superimposed optical pulse signal by superimposing a different low frequency modulation signal corresponding to the sum of a DC bias voltage and a modulation signal having a different frequency lower than the frequency of the clock signal on the optical pulse signal. When,
Photoelectrically converting the optical pulse signal obtained by multiplexing the low-frequency superimposed optical pulse signal into an electrical pulse signal;
Extracting a low frequency modulation component that is a frequency component equal to the low frequency modulation signal from the electrical pulse signal;
Mixing the low frequency modulation component and the low frequency modulation signal to generate a mixing signal;
And a step of removing a high-frequency component from the mixing signal and converting it to a DC voltage signal proportional to a peak value of an optical pulse constituting the optical pulse signal. A crest value control method of the optical pulses constituting the optical time division multiplex signal used time division multi Shigemichi the signal light by the synchronous detection,
An optical pulse train having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal is modulated with a modulation signal synchronized with the clock signal to generate an optical pulse signal for each N channel (N is a natural number of 2 or more). An optical pulse signal generation step to generate;
For every N channels,
A peak value detecting step of detecting a peak value of an optical pulse constituting the optical pulse signal by converting it to a DC voltage signal proportional to the peak value of the optical pulse;
For every N channels,
As a voltage value corresponding to the reference peak value, a voltage value corresponding to the difference between the reference voltage value set as the same value for all channels and the DC voltage signal detected in the peak value detection step is Crest value data generation step to generate as high value data;
For every N channels,
A crest value control step for controlling crest values of the optical pulses constituting the optical pulse signal so that the crest value data are all equal to each other,
The peak value detecting step includes
For every N channels,
A step of generating a low frequency superimposed optical pulse signal by superimposing a different low frequency modulation signal corresponding to the sum of a DC bias voltage and a modulation signal having a different frequency lower than the frequency of the clock signal on the optical pulse signal. When,
Photoelectrically converting the optical pulse signal obtained by multiplexing the low-frequency superimposed optical pulse signal into an electrical pulse signal;
Extracting a low frequency modulation component that is a frequency component equal to the low frequency modulation signal from the electrical pulse signal;
Bifurcating the low frequency modulation component into a first low frequency modulation component and a second low frequency modulation component;
Mixing the first low frequency modulation component and the low frequency modulation signal to generate a first mixing signal;
The phase of the low frequency modulation signal is delayed by 90 ° to generate a 90 ° delayed low frequency modulation signal, and the second low frequency modulation component and the 90 ° delayed low frequency modulation signal are mixed to generate a second mixing signal. Generating step;
A step of removing high frequency components from the first mixing signal and the second mixing signal, respectively, and converting each of the first voltage value and the second voltage value proportional to the peak value of the optical pulse constituting the optical pulse signal. When,
An optical pulse peak value control method comprising: generating a root mean square value of the first voltage value and the second voltage value as a DC voltage signal. In the optical pulse peak value control method according to claim 7 or 8,
The peak value data generation step includes
For every N channels,
Setting the reference voltage value;
Collecting a DC voltage signal proportional to the peak value of the optical pulse constituting the optical pulse signal;
And a step of generating, as peak value data, a voltage value corresponding to a difference between the collected DC voltage signal and the reference voltage value. A peak value control unit of the optical pulses constituting the optical time division multiplex signal used time division multi Shigemichi the signal light by the synchronous detection,
An optical pulse train having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal is modulated with a modulation signal synchronized with the clock signal to generate an optical pulse signal for each N channel (N is a natural number of 2 or more). An optical pulse signal generation unit to generate,
A peak value detector that detects the peak value of the optical pulse that constitutes the optical pulse signal by converting the peak value of the optical pulse into a DC voltage signal for each N channel proportional to the peak value of the optical pulse;
As a voltage value corresponding to the reference peak value, a voltage value for each N channel corresponding to the difference between the reference voltage value set as the same value for all channels and the DC voltage signal is generated as peak value data. A peak value data generator,
A bias voltage control unit that controls the peak value of the optical pulse constituting the optical pulse signal for each N channel so that the peak value data for each N channel are equal to each other,
The peak value detector is
For every N channels,
Variable light that generates a low-frequency superimposed optical pulse signal by superimposing a different low-frequency modulation signal corresponding to the sum of a DC bias voltage and a modulation signal having a different frequency lower than the frequency of the clock signal on the optical pulse signal An attenuator,
A photoelectric converter that photoelectrically converts an optical pulse signal obtained by multiplexing the low-frequency superimposed optical pulse signal into an electrical pulse signal;
A first filter that extracts a low frequency modulation component that is a frequency component equal to the low frequency modulation signal from the electrical pulse signal;
A mixer that mixes the low frequency modulation component and the low frequency modulation signal to generate a mixing signal;
An optical pulse peak value control comprising: a second filter that removes a high-frequency component from the mixing signal and converts it into a DC voltage value signal proportional to the peak value of the optical pulse constituting the optical pulse signal. apparatus. A peak value control unit of the optical pulses constituting the optical time division multiplex signal used time division multi Shigemichi the signal light by the synchronous detection,
An optical pulse train having a repetition frequency equal to the frequency of the clock signal and synchronized with the clock signal is modulated with a modulation signal synchronized with the clock signal to generate an optical pulse signal for each N channel (N is a natural number of 2 or more). An optical pulse signal generation unit to generate,
A peak value detector that detects the peak value of the optical pulse that constitutes the optical pulse signal by converting the peak value of the optical pulse into a DC voltage signal for each N channel proportional to the peak value of the optical pulse;
As a voltage value corresponding to the reference peak value, a voltage value for each N channel corresponding to the difference between the reference voltage value set as the same value for all channels and the DC voltage signal is generated as peak value data. A peak value data generator,
A bias voltage control unit that controls the peak value of the optical pulse constituting the optical pulse signal for each N channel so that the peak value data for each N channel are equal to each other,
The peak value detector is
For every N channels,
Variable light that generates a low-frequency superimposed optical pulse signal by superimposing a different low-frequency modulation signal corresponding to the sum of a DC bias voltage and a modulation signal having a different frequency lower than the frequency of the clock signal on the optical pulse signal An attenuator,
A photoelectric converter that photoelectrically converts an optical pulse signal obtained by multiplexing the low-frequency superimposed optical pulse signal into an electrical pulse signal;
A first filter that extracts a low frequency modulation component that is a frequency component equal to the low frequency modulation signal from the electrical pulse signal;
A branching device bifurcating the low frequency modulation component into a first low frequency modulation component and a second low frequency modulation component;
A first mixer that mixes the first low frequency modulation component and the low frequency modulation signal to generate a first mixing signal;
A second mixer that generates a second mixing signal by mixing the second low-frequency modulation component and a delayed low-frequency modulation signal delayed by 90 ° with respect to the phase of the low-frequency modulation signal;
A high-frequency component is removed from each of the first mixing signal and the second mixing signal, and converted into a first voltage value and a second voltage value that are proportional to the peak value of the optical pulse constituting the optical pulse signal, respectively. 2 filters and a third filter;
An optical pulse peak value control device comprising: a mean square value generating unit that generates a DC voltage signal that is a mean square value of the first voltage value and the second voltage value. In the optical pulse peak value control device according to claim 10 or 11,
The peak value data generation unit
For every N channels,
An initial value data storage unit for storing the reference voltage value set as a voltage value corresponding to a reference peak value;
A data collection unit for collecting a DC voltage signal proportional to the peak value of the optical pulse constituting the optical pulse signal;
An optical pulse peak value control apparatus comprising: a data processing unit that generates a voltage value corresponding to a difference between the collected DC voltage signal and the reference voltage value as peak value data. A peak value automatic control method of the optical pulses constituting the optical time division multiplex signal used time division multi Shigemichi the signal light by the synchronous detection,
A first step of manually setting a temporary voltage value in a DC voltage setting circuit that supplies a DC bias voltage to a variable optical attenuator that superimposes a low frequency modulation signal on an optical pulse signal;
The peak value of the optical pulse signal is observed by the waveform monitor to determine whether or not the observed value is within the design value range. If the peak value is not within the design value range, the process returns to the first step. ,
If the peak value is within a design value range, a second step of manually setting the temporary voltage value as an initial voltage value in the DC voltage setting circuit;
A third step of manually setting the initial voltage value in the DC voltage setting circuit;
The fourth step of inputting the output data output from the voltage output unit first after the third step to the initial value data storage unit by computer control,
The fifth step of inputting output data output from the voltage output unit after the third step after the third step is input to the data collection unit by computer control,
A sixth step of calculating by computer control the difference between the output data of the voltage output unit input to the data collection unit and the output data of the voltage output unit input to the initial value data storage unit as peak value data; ,
The peak value data is determined by computer control as a positive value when the output data of the voltage output unit input to the data collection unit is larger than the initial voltage value, and as a negative value when smaller than the initial voltage value. Process,
If the peak value data is a negative value, an eighth step of changing the initial voltage value set in the DC voltage setting circuit by computer control so that the amount of optical loss of the variable optical attenuator decreases. When,
If the peak value data is a positive value, a ninth step of changing the initial voltage value set in the DC voltage setting circuit by computer control so that the optical loss amount of the variable optical attenuator increases. A method for automatically controlling the crest value of an optical pulse.

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