JP5009130B2 - Clock phase synchronization circuit and optical receiver - Google Patents

Description

  The present invention relates to a clock phase synchronization circuit and an optical receiver used when demultiplexing an optical time division multiplexed signal.

  By performing signal processing in the optical frequency domain when demultiplexing an optical time division multiplexed signal, a high-speed demultiplexing operation can be realized. As a method for realizing such demultiplexing operation, a configuration of an optical receiver as shown in FIG. 1 is known (for example, Non-Patent Document 1).

  As shown in FIG. 1A, a conventional optical receiver 101 includes a signal generator 102, a direct modulation light source 103 that outputs an optical signal that is directly frequency shift modulated by the output of the signal generator 102, and an optical receiver 101. The optical coupler 104 that combines the optical time division multiplexed signal input from the optical signal input unit and the optical signal output from the direct modulation light source 103, and the optical time division multiplexed signal combined by the optical coupler 104 And an optical detector 105 for optical heterodyne reception of an optical signal output from the direct modulation light source 103, an electric bandpass filter 106 that transmits a part of the band of the output signal of the optical detector 105, and an electric bandpass filter 106. An intermediate frequency signal demodulator 107 that demodulates the output and outputs a target signal is provided.

Here, FIG. 1B shows an example of the relationship between the time waveform of the signal and the frequency component in (a), (b), (c), and (d) in FIG. 1A. The time waveform of the optical time division multiplexed signal input from the optical signal input unit of the optical receiver 101 is (a) in FIG. 1B, and the signal channels α, β, γ, and δ are multiplexed. At this time, the frequency component of the optical time division multiplexed signal spreads from the center frequency f _S by the modulation speed f _B. In addition, the signal generator 102 and the direct modulation light source 103 cause the frequency to vary from −Δf to + Δf at a center frequency f _LO, constant intensity, and a quarter of the modulation speed f _B as shown in FIG. 1B (b). Output local oscillation light. Next, the optical time division multiplexed signal and the local oscillation light are multiplexed using the optical coupler 104. At this time, the frequency variation of the target signal channel α of the optical time division multiplexed signal and the local oscillation light becomes + Δf. Are combined so that the timings coincide. Thereafter, the optical detector 105 causes optical heterodyne reception, and an intermediate frequency signal in which the target signal channel α is shifted from the center frequency f _S −f _LO to the low frequency side by Δf as shown in FIG. Is output. By passing only the frequency component corresponding to the signal channel α among the frequency components of the intermediate frequency signal using the electric bandpass filter 106, only the target signal channel α is multiplexed as shown in FIG. 1B (d). The target signal channel α can be demodulated by demodulating the demultiplexed signal using the intermediate frequency signal demodulator 107.
Sei Narukawa, Naoya Sakurai, Hideaki Kimura, Shin Tsubokawa, "Demultiplexing method of OTDM signal using optical heterodyne reception", 2007 IEICE Society Conference B-10-61 (2007), September 13, 2007 Day

  The conventional optical receiver shown in FIG. 1 is capable of demultiplexing a high-speed optical time division multiplexed signal with a simple configuration, while the frequency-shifted modulation signal output from the signal generator 102 and the direct modulation light source 103 is used. It is necessary to strictly match the modulation timing with the target signal channel of the optical time division multiplexed signal. For this reason, the clock component of the optical time division multiplexed signal is required. However, in the conventional configuration, clock phase synchronization is not performed on the optical receiver side, so the clock signal is transmitted from the transmitter separately from the optical time division multiplexed signal. Therefore, it is difficult to construct an optical transmission system economically.

  An object of the present invention is to provide an economical optical receiver by realizing a clock phase synchronization circuit at the time of optical time division multiplexed signal reception without largely changing the configuration of the optical receiver on the optical receiver side.

According to a first aspect of the present invention,
In the clock phase synchronization circuit used when demultiplexing and receiving optical time division multiplexed signals,
Signal generating means for generating a signal phase-synchronized by the clock phase synchronization circuit ;
An optical signal output means for outputting an optical signal directly frequency shift modulated by the signal generating means;
Optical multiplexing means for multiplexing the optical time division multiplexed signal and the direct frequency shift keying signal output from the optical signal output means;
Optical receiving means for optical heterodyne reception of the optical time division multiplexed signal and direct frequency shift keying signal combined by the optical multiplexing means;
Of the signals output from the optical receiving means, the difference between the center frequency of the optical time division multiplexed signal and the center frequency of the optical signal output from the optical signal output means is only ½ of the signal speed of the optical time division multiplexed signal. Transmission means for transmitting signals of shifted electrical frequencies ;
Comprising intensity detection means for intensity detection of the output of the transmission means,
Said intensity Ri by the output of the detection means, the transmitting means transmits the optical time division multiplex signal center frequency and the optical signal output means signal of the optical time division multiplex signal from the difference between the center frequency of the optical signal output from the The phase of the output signal of the signal generating means is controlled so that the signal of the electrical frequency shifted by ½ of the speed becomes maximum .

According to a second aspect of the present invention,
In the clock phase synchronization circuit used when demultiplexing and receiving optical time division multiplexed signals,
Light output means for outputting continuous light;
Signal generating means for generating a signal phase-synchronized by the clock phase synchronization circuit ;
Light modulation means for frequency shift modulation or phase shift modulation of the continuous light output from the light output means by the output of the signal generation means;
Optical multiplexing means for multiplexing the optical time division multiplexed signal and the frequency shift modulation signal or phase shift modulation signal output from the optical modulation means;
Optical receiving means for optical heterodyne reception of the optical time division multiplexed signal combined with the optical multiplexing means and the frequency shift modulation signal or phase shift modulation signal;
Of the signals output from the optical receiving means, the difference between the center frequency of the optical time division multiplexed signal and the center frequency of the optical signal output from the optical output means is shifted by 1/2 of the signal speed of the optical time division multiplexed signal. Transmitting means for transmitting a signal of electrical frequency ,
Comprising intensity detection means for intensity detection of the output of the transmission means,
Ri by the output of said intensity detecting means, the transmitting means transmits the signal speed of the optical time division multiplex signal from the difference between the center frequency of the center frequency and the optical signal optical output means outputs the optical time division multiplex signal The phase of the output signal of the signal generating means is controlled so that the signal with the electrical frequency shifted by ½ is maximized .

  A third aspect of the present invention is characterized in that the optical receiving means has a differential reception type optical detector.

According to a fourth aspect of the present invention,
In an optical receiver for demultiplexing and receiving optical time division multiplexed signals,
Signal generating means for generating a signal synchronized in phase with the optical receiver;
An optical signal output means for outputting an optical signal subjected to frequency shift keying or phase shift keying by the output of the signal generating means;
Optical multiplexing means for multiplexing the optical time division multiplexed signal and the frequency shift keying signal or phase shift keying signal output from the optical signal output means;
Optical receiving means for optical heterodyne reception of the optical time division multiplexed signal combined with the optical multiplexing means and the frequency shift modulation signal or phase shift modulation signal;
First transmission means for transmitting a signal having a frequency corresponding to a signal to be demultiplexed among the intermediate frequency signals output from the optical reception means;
Demodulation means for demodulating the output of the first transmission means;
1/2 from the difference between the center frequency of the optical signal output from the central frequency and the optical signal output means of the optical time division multiplex signal out of the signal output from the light receiving means of the signal speed of the optical time division multiplex signal A second transmission means for transmitting a signal having an electrical frequency shifted by
Comprising intensity detecting means for intensity detecting the output of the second transmitting means,
The optical time division multiplex signal is obtained from the difference between the center frequency of the optical time division multiplex signal transmitted by the second transmission means and the center frequency of the optical signal output from the optical signal output means by the output of the intensity detection means. The phase of the output signal of the signal generating means is controlled so that the signal of the electrical frequency shifted by ½ of the signal speed becomes maximum.

According to a fifth aspect of the present invention,
In an optical receiver for demultiplexing and receiving optical time division multiplexed signals,
Signal generating means for generating a signal synchronized in phase with the optical receiver;
An optical signal output means for outputting an optical signal subjected to frequency shift keying or phase shift keying by the output of the signal generating means;
Optical multiplexing means for multiplexing the optical time division multiplexed signal and the frequency shift keying signal or phase shift keying signal output from the optical signal output means;
First optical receiving means for optical heterodyne reception of the optical time division multiplexed signal combined with the optical multiplexing means and a part of the frequency shift keying signal or phase shift keying signal;
First transmission means for transmitting a signal having a frequency corresponding to a signal to be demultiplexed among the intermediate frequency signals output from the first optical reception means;
Demodulation means for demodulating the output of the first transmission means;
Second optical receiving means for optically heterodyne receiving a part of the optical time division multiplexed signal combined with the optical multiplexing means and the frequency shift keying signal or phase shift keying signal;
From the difference between the center frequency of the optical signal output from the central frequency and the optical signal output means of the optical time division multiplex signal of the signal output from the second light receiving means of the signal speed of the optical time division multiplex signal A second transmission means for transmitting a signal having an electrical frequency shifted by ½,
Comprising intensity detecting means for intensity detecting the output of the second transmitting means,
The optical time division multiplex signal is obtained from the difference between the center frequency of the optical time division multiplex signal transmitted by the second transmission means and the center frequency of the optical signal output from the optical signal output means by the output of the intensity detection means. The phase of the output signal of the signal generating means is controlled so that the signal of the electrical frequency shifted by ½ of the signal speed becomes maximum.

According to a sixth aspect of the present invention,
In an optical receiver for demultiplexing and receiving optical time division multiplexed signals,
First optical branching means for branching the optical time division multiplexed signal;
Signal generating means for generating a signal synchronized in phase with the optical receiver;
An optical signal output means for outputting an optical signal subjected to frequency shift keying or phase shift keying by the output of the signal generating means;
Second optical branching means for branching the output optical signal of the optical signal output means;
At least one optical delay means for providing an optical delay to the output optical signal of the second optical branching means;
First optical coupling means for combining the output optical signal of the second optical branching means and the output optical signal of the first optical branching means;
Provided corresponding to the optical delay means, and at least one second optical coupling means for multiplexing the output optical signal of the optical delay means and the output optical signal of the first optical branching means;
A plurality of optical receiving means provided corresponding to the first and second optical coupling means, for optically heterodyne-receiving the output optical signal combined by the first and second optical coupling means;
A plurality of demodulation means that are provided corresponding to the plurality of optical receiving means and demodulate using a signal of a frequency corresponding to a signal to be demultiplexed among the intermediate frequency signals output from the optical receiving means;
Is connected to one of said plurality of light receiving means, the center frequency of the optical signal output from the central frequency and the optical signal output means of the optical time division multiplex signal of the signal output from the light receiving means Phase control signal extraction means for extracting a phase control signal using a signal having an electrical frequency shifted from the difference by 1/2 of the signal speed of the optical time division multiplexed signal,
Due to the phase control signal output from the phase control signal extraction means, the signal speed of the optical time division multiplexed signal is calculated from the difference between the center frequency of the optical time division multiplexed signal and the center frequency of the optical signal output from the optical signal output means. The phase of the output signal of the signal generating means is controlled so that the signal with the electrical frequency shifted by ½ is maximized.

According to a seventh aspect of the present invention, in the fourth or sixth aspect, the optical receiving means includes a differential reception type optical detector.

According to an eighth aspect of the present invention, in the fifth aspect, the first and second optical receiving means include a differential reception type optical detector.

  According to the first aspect of the present invention, a phase error signal of a clock component of an optical time division multiplexed signal transmitted at high speed can be extracted by optical heterodyne reception using frequency shift modulated light as local oscillation light. By controlling the signal generating means using this phase error signal, it becomes possible to demultiplex and receive the target channel stably.

  According to the second aspect of the present invention, the phase error of the clock component of the optical time division multiplexed signal transmitted at high speed by the optical heterodyne reception using the frequency shift modulated light or the phase shift modulated light as the local oscillation light. It becomes possible to extract a signal, and by controlling the signal generating means using this phase error signal, it becomes possible to stably demultiplex and receive the target channel.

  According to the third aspect of the present invention, in the clock phase synchronization circuit of the first or second aspect, it becomes possible to remove the baseband component of the optical time division multiplexed signal generated when optical heterodyne reception is performed. Thus, it is possible to configure a clock phase synchronization circuit with higher reception characteristics.

  According to the fourth aspect of the present invention, in the clock phase synchronization circuit according to the first to third aspects, it is possible to receive the phase error signal with high sensitivity and to realize a more accurate clock phase synchronization operation. It becomes possible.

  According to the fifth aspect of the present invention, it is possible to perform demultiplexing and clock phase synchronization of an optical time division multiplexed signal in a configuration in which the signal generating means and the optical signal output means are shared by the optical receiver and the clock phase synchronization circuit. This makes it possible to realize a stable demultiplexing operation without using an expensive and complicated configuration including an optical amplifier and a phase modulator.

  According to the sixth aspect of the present invention, as in the fifth aspect, the optical time division multiplexed signal is demultiplexed in a configuration in which the signal generating means and the optical signal output means are shared by the optical receiver and the clock phase synchronization circuit. The clock phase synchronization can be performed, and a stable demultiplexing operation can be realized without using an expensive and complicated configuration including an optical amplifier and a phase modulator. Furthermore, by arranging a plurality of optical receiving means, it becomes possible to individually optimize the characteristics of the optical receiving means for the signal demultiplexing operation and the clock phase synchronization operation, thereby configuring an optical receiver with higher receiving characteristics. It becomes possible.

  According to the seventh aspect of the present invention, when a plurality of signal channels are simultaneously demultiplexed and received, it is not necessary to separately provide a clock phase synchronization circuit in the demultiplexing and receiving unit. Is possible.

  According to the eighth aspect of the present invention, in the optical receivers of the fifth to seventh aspects, it becomes possible to remove the baseband component of the optical time division multiplexed signal generated when optical heterodyne reception is performed, An optical receiver with higher reception characteristics can be configured.

  According to the ninth aspect of the present invention, in the optical receivers of the fifth to eighth aspects, it is possible to receive the phase error signal with high sensitivity, and to realize a more accurate clock phase synchronization operation. Is possible.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 2 is a diagram showing the configuration of the clock phase synchronization circuit according to the first embodiment of the present invention. As shown in FIG. 2A, the clock phase synchronization circuit 201 according to the first embodiment outputs a signal generator 202 as signal generating means and an optical signal that is directly frequency shift modulated by the signal generator 202. A direct modulation light source 203 as an optical signal output means, an optical time division multiplexed signal input from the optical signal input unit of the clock phase synchronization circuit 201, and a direct frequency shift keying signal output from the direct modulation light source 203 are combined. An optical coupler 204 as an optical multiplexing means, an optical detector 205 as an optical receiving means for optical heterodyne reception of the optical time division multiplexed signal and the direct frequency shift keying signal multiplexed by the optical coupler 204, An electric bandpass filter 206 as a transmission means that transmits a part of the output of the detector 205, and an intensity detection means for intensity detection of the output of the electric bandpass filter 206; Comprising a strength detector 207 of Te.

  In the first embodiment, the phase of the output signal of the signal generator 202 is controlled by the output of the intensity detector 207, and the signal generator 202 can be configured using, for example, an oscillator and an electric amplifier.

Here, FIG. 2B and FIG. 2C show an example of the relationship between the time waveform of the signal and the frequency component in (a), (b), and (c) in FIG. 2A. The time waveform of the optical time division multiplexed signal input from the optical signal input unit of the clock phase synchronization circuit 201 is (a) in FIG. 2B or 2C, and the signal channels α, β, γ, and δ are multiplexed. Yes. At this time, the frequency component of the optical time division multiplexed signal spreads from the center frequency f _S by the modulation speed f _B. Further, the signal generator 202 and the direct modulation light source 203 allow the frequency to be −Δf at a center frequency f _LO, constant intensity, and 1/4 of the modulation speed f _B as shown in FIG. 2B or 2B (b). The local oscillation light which fluctuates up to + Δf is output.

  Next, the optical time division multiplexed signal and the local oscillation light are multiplexed using the optical coupler 204. At this time, as shown in FIG. 2B (b), the target signal channel α and the local part of the optical time division multiplexed signal are combined. By multiplexing so that the timing when the frequency fluctuation of the oscillation light becomes + Δf is coincident, the demultiplexing operation of the optical time division multiplexed signal can be realized. However, as shown in FIG. 2C (b), for example, the target signal channel α of the optical time division multiplexed signal does not coincide with the timing at which the frequency fluctuation of the local oscillation light becomes + Δf, and the frequency fluctuation of the local oscillation light + Δf In such a case, the signal cannot be demultiplexed if the timing becomes the same as the timing corresponding to the channel interval of the optical time division multiplexed signal.

At this time, when comparing the frequency component of the FIG. 2B (c) and FIG. _{2C (c), f S -f} LO frequency components of the frequency components or _f S _{-f LO} ± _{f B} is, demultiplexing operation is feasible It can be seen that the size is smaller in the case of FIG. 2B and larger in the case of FIG. 2C where the demultiplexing operation cannot be performed. Furthermore, the frequency component of f _S -f _LO ± f _B / 2 or the frequency component of f _S -f _LO ± 3 f _B / 2 becomes large in the case of FIG. It can be seen that in the case of FIG.

Therefore, the electrical band-pass filter _206, f S _-f frequency component of the _LO, f S _{-f LO} frequency components of _{± f B, f S -f LO} ± f B / 2 of the frequency components or _f S -f _After passing through any single frequency component of the frequency components of _LO ± 3 f _B / 2 and extracting the intensity component by the intensity detector 207, this intensity component becomes the frequency component of f _S −f _LO or f _S −. The phase of the output signal of the signal generator 202 is controlled so as to be minimized when the frequency component of f _LO ± f _B is transmitted, and the frequency component of f _S −f _LO ± f _B / 2 or f By controlling the phase of the output signal of the signal generator 202 so as to be maximized when the frequency component of _S −f _LO ± 3f _B / 2 is transmitted, the optical time division multiplexed signal and the local part are optimally controlled. Combine oscillation light Is possible.

In the configuration of FIG. 2A, FIGS. 2B and 2C show a case where the electric bandpass filter 206 transmits the frequency component of f _S −f _LO −f _B / 2.

  With the configuration as in the first embodiment, the phase of the output signal of the signal generator is controlled by the output of the intensity detector 207, so that the clock phase synchronization operation of the optical time division multiplexed signal transmitted at high speed Can be realized using components having a relatively low frequency compared to the signal speed.

  In addition, since photoelectric conversion is performed using optical heterodyne reception, frequency components necessary for clock phase synchronization can be received with high sensitivity, and it is not necessary to use complicated optical components such as an optical amplifier.

  Further, since the demultiplexing is performed by using more economical electrical components than optical components, it is not necessary to perform the clock phase synchronization operation in the optical frequency domain, and an economical clock phase synchronization circuit can be configured.

  FIG. 3 is a diagram showing a configuration of a clock phase synchronization circuit according to the second embodiment of the present invention. As shown in FIG. 3, a clock phase synchronization circuit 301 according to the second embodiment includes a light source 302 as an optical output unit that outputs continuous light, a signal generator 303 as a signal generation unit, and a signal generator 303. The optical modulator 304 as optical modulation means for frequency shift modulation or phase shift modulation of the continuous light output from the light source 302, and the time of light input from the optical signal input unit of the clock phase synchronization circuit 301 An optical coupler 305 as optical multiplexing means for multiplexing the division multiplexed signal and the frequency shift modulation signal or phase shift modulation signal output from the optical modulator 304, and the time of the light combined by the optical coupler 305 An optical detector 306 as optical receiving means for optical heterodyne reception of the division multiplexed signal and frequency shift keying signal or phase shift keying signal, and transmission means for transmitting a part of the output of the optical detector 306 Comprising the electrical band-pass filter 307, an intensity detector 308 of the output of the electrical band-pass filter 307 as the intensity detecting means for intensity detection.

  According to the second embodiment, the phase of the output signal of the signal generator 303 is controlled by the output of the intensity detector 308, and the signal generator 303 can be configured using, for example, an oscillator and an electric amplifier. is there.

  The operation principle in the second embodiment is the same as that in the first embodiment. By adopting the configuration as in the second embodiment, the phase of the output signal of the signal generator 303 is controlled by the output of the intensity detector 308, so that the clock phase synchronization of the optical time division multiplexed signal transmitted at high speed is achieved. The operation can be realized by using a component having a relatively low frequency compared to the signal speed.

  In addition, since photoelectric conversion is performed using optical heterodyne reception, frequency components necessary for clock phase synchronization can be received with high sensitivity, and it is not necessary to use complicated optical components such as an optical amplifier.

  Further, since the demultiplexing is performed by using more economical electrical components than optical components, it is not necessary to perform the clock phase synchronization operation in the optical frequency domain, and an economical clock phase synchronization circuit can be configured.

  In general, intensity modulation components are generated during high-speed modulation, but the number of optical components is increased compared to a direct modulation light source with a limited modulation speed. The clock phase synchronization operation can be realized.

  FIG. 4 is a diagram showing a configuration of a clock phase synchronization circuit according to the third embodiment of the present invention. As shown in FIG. 4, the clock phase synchronization circuit 401 according to the third embodiment includes a signal generator 402 as a signal generation unit, and an optical signal that outputs an optical signal that is directly frequency shift modulated by the signal generator 402. A direct modulation light source 403 serving as a signal output unit, an optical time division multiplexed signal input from the optical signal input unit of the clock phase synchronization circuit 401, and a direct frequency shift keying signal output from the direct modulation light source 403 are combined. An optical coupler 404 as optical multiplexing means, and a differential reception type optical detector 405 as optical receiving means for optical heterodyne reception of the optical time division multiplexed signal and direct frequency shift keying signal combined by the optical coupler 404. And an electric bandpass filter 406 as a transmission means that transmits a part of the output of the differential reception type optical detector 405, and intensity detection of the output of the electric bandpass filter 406 Comprising an intensity detector 407 as intensity detection means.

  In the third embodiment, the phase of the output signal of the signal generator 402 is controlled by the output of the intensity detector 407, and the signal generator 402 can be configured using, for example, an oscillator and an electric amplifier.

  The operation principle in the third embodiment is the same as that in the first embodiment. As in the second embodiment, a continuous light source and an external modulator can be used instead of the direct modulation light source 403.

  By adopting the configuration as in the third embodiment, it is possible to realize the clock phase synchronization operation of the optical time division multiplexed signal transmitted at high speed by using components having a relatively low frequency compared to the signal speed. It becomes.

  In addition, since photoelectric conversion is performed using optical heterodyne reception, frequency components necessary for clock phase synchronization can be received with high sensitivity, and it is not necessary to use complicated optical components such as an optical amplifier.

  Further, since the demultiplexing is performed by using more economical electrical components than optical components, it is not necessary to perform the clock phase synchronization operation in the optical frequency domain, and an economical clock phase synchronization circuit can be configured.

  Further, by using a differential reception type optical detector at the time of optical heterodyne reception, there is no coupling loss generated when signals are combined in the optical coupler 404, and the direct reception component of the optical time division multiplexed signal is canceled out. Therefore, the phase error signal component can be received with high sensitivity, and the intermediate frequency signal generated after the optical detection can be shifted to the lower frequency side, so that the desired band of the optical detector and the electrical parts can be reduced. This makes it possible to contribute to an economical receiver configuration.

  FIG. 5 is a diagram showing a configuration of an optical receiver according to the fourth embodiment of the present invention. As shown in FIG. 5, the optical receiver 501 according to the fourth embodiment includes a signal generator 502 as signal generation means, and light that has been frequency-shift-modulated or phase-shift-modulated by the output of the signal generator 502. A modulated light source 503 as an optical signal output means for outputting a signal; an optical time division multiplexed signal input from the optical signal input unit of the optical receiver 501; and a frequency shift modulated signal or phase shift output from the modulated light source 503. Optical coupler 504 as optical multiplexing means for multiplexing the modulation signal, and light for optical heterodyne reception of the optical time division multiplexed signal combined with optical coupler 504 and the frequency shift modulation signal or phase shift modulation signal An optical detector 505 as a receiving means, an electric bandpass filter 506 as a first transmitting means that transmits part of the output of the optical detector 505, and an output of the electric bandpass filter 506 are demodulated. A demodulating circuit 507 as a demodulating unit, an electric bandpass filter 508 as a second transmitting unit that transmits a part of the output of the optical detector 505, and an intensity detecting unit that detects the intensity of the output of the electric bandpass filter 508 The intensity detector 509 is provided.

  In the fourth embodiment, the phase of the output signal of the signal generator 502 is controlled by the output of the intensity detector 509, and the signal generator 502 can be configured using, for example, an oscillator and an electric amplifier.

  The modulated light source 503 can be configured using a direct modulation light source or a continuous light source and an external modulator as in the first to third embodiments. Further, the optical detector 505 can be configured using a differential reception type optical detector instead of the optical detector as in the third embodiment.

  The operation principle of the fourth embodiment is the same as that of the first embodiment in the operation of the clock phase synchronization circuit, and the demultiplexing operation of the optical time division multiplexed signal is the same as that in the prior art. By adopting the configuration as in the fourth embodiment, the phase of the output signal of the signal generator is controlled by the output of the intensity detector 509, so that the clock phase synchronization operation and the demultiplexing operation of the optical time division multiplexed signal are performed. This can be realized simultaneously using components having a relatively low frequency compared to the signal speed.

  Further, since the signal generator 502, the modulation light source 503, the optical coupler 504, and the optical detector 505 can be shared by the clock phase synchronization operation and the optical time division multiplexed signal demultiplexing operation, it is economical. An optical receiver can be configured according to the configuration.

  FIG. 6 is a diagram showing a configuration of an optical receiver according to the fifth embodiment of the present invention. As shown in FIG. 6, the optical receiver 601 according to the fifth embodiment includes a signal generator 602 serving as a signal generating unit, and light that is frequency-shift modulated or phase-shift modulated by the output of the signal generator 602. A modulated light source 603 serving as an optical signal output means for outputting a signal; an optical time-division multiplexed signal input from the optical signal input unit of the optical receiver 601; and a frequency shift modulated signal or phase shift output from the modulated light source 603. An optical coupler 604 as optical multiplexing means for multiplexing the modulation signal, and an optical time-division multiplexed signal combined with the optical coupler 604 and a part of the frequency shift keying signal or phase shift keying signal are optical heterodyne. An optical detector 605 as a first optical receiving means for receiving, an electric bandpass filter 606 as a first transmitting means for transmitting a part of the output of the optical detector 605, and an electric bandpass filter 606. A demodulating circuit 607 as a demodulating means for demodulating the power, and a second optical heterodyne receiving optical time division multiplexed signal combined with the optical coupler 604 and a part of the frequency shift keying signal or phase shift keying signal. An optical detector 608 as an optical receiving means, an electric bandpass filter 609 as a second transmission means that transmits a part of the output of the optical detector 608, and an intensity detection that detects the output of the electric bandpass filter 609 in intensity. An intensity detector 610 is provided as a means.

  In the fifth embodiment, the phase of the output signal of the signal generator 602 is controlled by the output of the intensity detector 610, and the signal generator 602 can be configured using, for example, an oscillator and an electric amplifier.

  The modulated light source 603 can be configured using a direct modulation light source or a continuous light source and an external modulator as in the first to fourth embodiments. Moreover, the optical detectors 605 and 608 can be configured using a differential reception type optical detector instead of the optical detector, as in the third embodiment.

  The operation principle in the fifth embodiment is the same as that of the first embodiment in the operation of the clock phase synchronization circuit, and the demultiplexing operation of the optical time division multiplexed signal is the same as in the case of the prior art. By adopting the configuration as in the fifth embodiment, the clock phase synchronization operation and the demultiplexing operation of the optical time division multiplexed signal can be realized at the same time by using relatively low frequency components compared to the signal speed. It becomes possible.

  Further, since the signal generator 502, the modulation light source 503, and the optical coupler 504 can be shared by the clock phase synchronization operation and the demultiplexing operation of the optical time division multiplexed signal, the optical receiver has an economical configuration. Can be configured.

  Furthermore, by arranging a plurality of optical detectors, it is possible to individually optimize the characteristics of the optical detectors for the signal demultiplexing operation and the clock phase synchronization operation, thereby configuring an optical receiver with higher reception characteristics. It becomes possible.

  FIG. 7 is a diagram showing a configuration of an optical receiver according to the sixth embodiment of the present invention. As shown in FIG. 7, an optical receiver 701 according to the sixth embodiment includes an optical splitter 702 as a first optical branching unit that branches the optical time division multiplexed signal input from the optical receiver 701, A signal generator 703 as a signal generation unit, a modulation light source 704 as an optical signal output unit that outputs an optical signal that is frequency-shift-modulated or phase-shift-modulated by the output of the signal generator 703, and an output of the modulation light source 704 An optical branching unit 705 as a second optical signal branching unit for branching the optical signal, and a plurality of optical delay units 706-2 to 706-4 as an optical delaying unit for giving an optical delay to the output optical signal of the optical branching unit 705. An optical coupler 707-1 as first optical multiplexing means for combining the output optical signal of the optical splitter 702 and the output optical signal of the optical splitter 705, and the output optical signal and light of the optical splitter 702 Delay devices 706-2 to 706-4 Receiving the outputs of the optical couplers 707-2 to 707-4 and the optical couplers 707-1 to 707-4 as second optical multiplexing means for multiplexing the respective output optical signals, the signals are demodulated. Phase control as phase control signal extraction means for receiving one of the outputs of optical receiving sections 708-1 to 708-4 as demodulation means and optical couplers 707-1 to 707-4 and extracting a phase control signal Part 709.

  In the sixth embodiment, the phase of the output signal of the signal generator 703 is controlled by the output of the phase control unit 709, and the signal generator 703 can be configured using, for example, an oscillator and an electric amplifier.

  The modulated light source 704 can be configured using a direct modulation light source or a continuous light source and an external modulator as in the first to third embodiments. In addition, as in the fourth or fifth embodiment, the optical receivers 708-1 to 708-4 include an optical detector, an electric bandpass filter, an intermediate frequency signal demodulator, a differential reception type optical detector, and an electric detector. The phase control unit 709 can be configured by using a bandpass filter and an intermediate frequency signal demodulator, and the phase control unit 709 can be configured by using an optical detector, an electric bandpass filter, an intensity detector, or a difference as in the first to fifth embodiments. It can be configured using a dynamic reception type optical detector, an electric bandpass filter, and an intensity detector.

  In FIG. 7, the phase control unit 709 is connected to the output of the optical coupler 707-4, but the same effect can be obtained by connecting to any of the optical couplers 707-1 to 707-3. .

  Further, as in the fifth embodiment, the optical detector can be shared by the optical receiver 708 and the phase controller 709. In this case, the operation principle of the sixth embodiment is that the operation of the clock phase synchronization circuit is the same as that of the first embodiment, and the demultiplexing operation of the optical time division multiplexed signal is the same as that of the prior art. It is.

  When receiving an optical signal, the signal is branched to a plurality of receiving units, and the timing of frequency fluctuation of the local oscillation light is made to coincide with the signal channel to be received using the optical delay units 706-2 to 706-4. Multiple signal channels can be received at the same time. Furthermore, only one clock phase synchronization circuit unit needs to be prepared for all signal channel reception units, so the clock phase synchronization circuit unit can be shared. An economical optical receiver can be constructed.

  As described above, the present invention makes it possible to reduce the number of parts by using both the optical domain and electrical domain signal processing in the clock phase synchronization circuit at the time of optical time division multiplexed signal reception. Since it is possible to share parts with the demultiplexing circuit of the multiplexed signal, the optical receiver including the clock phase synchronization circuit can be realized with an economical configuration.

In the clock phase synchronization circuit of the first to third embodiments or the optical receiver of the fourth to seventh embodiments, as shown in FIGS. 2B (c) and 2C (c), the clock phase The transmission band of the electric bandpass filter included in the synchronization circuit is set so as to transmit the frequency component of f _S −f _LO ± f _B / 2.

Here, when the demultiplexing operation is possible, that is, as shown in FIG. 2B, when the target signal channel of the optical time division multiplexed signal and the timing at which the frequency fluctuation of the local oscillation light becomes + Δf coincide, _When the frequency component of _S −f _LO ± f _B / 2 is output larger than the other frequency components and demultiplexing operation is impossible, that is, the target signal channel of the optical time division multiplexed signal and the frequency of the local oscillation light when the timing change is + Delta] f it is temporally shifted f _{B /} 2 _{is, f S -f LO ± f B} / 2 of the frequency components are smaller output than the other frequency components.

Therefore, by transmitting the frequency component of f _S −f _LO ± f _B / 2 with an electric bandpass filter, the difference in intensity of the phase error signal between when the demultiplexing operation is possible and when it is impossible can be obtained. Therefore, it is possible to realize a highly sensitive clock phase synchronization circuit.

It is a figure which shows a prior art. It is a figure explaining the operation principle of a prior art. It is a figure which shows the 1st Example of this invention. It is a figure explaining the principle of operation of the 1st example. It is a figure explaining the principle of operation of the 1st example. It is a figure which shows the 2nd Example of this invention. It is a figure which shows the 3rd Example of this invention. It is a figure which shows the 4th Example of this invention. It is a figure which shows the 5th Example of this invention. It is a figure which shows the 6th Example of this invention.

Explanation of symbols

101, 501, 601, 701 Optical receivers 102, 202, 303, 402, 502, 602, 703 Signal generators 103, 203, 403 Directly modulated light sources 104, 204, 305, 404, 504, 604, 707-1, 707-2, 707-3, 707-4 Optical couplers 105, 205, 306, 405, 505, 605, 608 Optical detectors 106, 206, 307, 406, 506, 508, 606, 609 Electric bandpass filter 107 , 507, 607 Intermediate frequency signal demodulator 201, 301, 401 Clock phase synchronization circuit 207, 308, 407, 509, 610 Intensity detector 302 Light source 304 External modulator 503, 603, 704 Modulated light source 702, 705 Optical splitter 706 -2, 706-3, 706-4 Optical delay devices 708-1, 708-2 708-3,708-4 optical receiver 709 phase controller

Claims (8)

In the clock phase synchronization circuit used when demultiplexing and receiving optical time division multiplexed signals,
Signal generating means for generating a signal phase-synchronized by the clock phase synchronization circuit;
An optical signal output means for outputting an optical signal directly frequency shift modulated by the signal generating means;
Optical multiplexing means for multiplexing the optical time division multiplexed signal and the direct frequency shift keying signal output from the optical signal output means;
Optical receiving means for optical heterodyne reception of the optical time division multiplexed signal and direct frequency shift keying signal combined by the optical multiplexing means;
Of the signals output from the optical receiving means, the difference between the center frequency of the optical time division multiplexed signal and the center frequency of the optical signal output from the optical signal output means is only ½ of the signal speed of the optical time division multiplexed signal. Transmission means for transmitting signals of shifted electrical frequencies;
Comprising intensity detection means for intensity detection of the output of the transmission means,
Based on the difference between the center frequency of the optical time division multiplexed signal transmitted by the transmission means and the center frequency of the optical signal output by the optical signal output means, the signal speed of the optical time division multiplexed signal is transmitted by the output of the intensity detection means. A clock phase synchronization circuit, wherein the phase of an output signal of the signal generating means is controlled so that a signal having an electrical frequency shifted by ½ is maximized. In the clock phase synchronization circuit used when demultiplexing and receiving optical time division multiplexed signals,
Light output means for outputting continuous light;
Signal generating means for generating a signal phase-synchronized by the clock phase synchronization circuit;
Light modulation means for frequency shift modulation or phase shift modulation of the continuous light output from the light output means by the output of the signal generation means;
Optical multiplexing means for multiplexing the optical time division multiplexed signal and the frequency shift modulation signal or phase shift modulation signal output from the optical modulation means;
Optical receiving means for optical heterodyne reception of the optical time division multiplexed signal combined with the optical multiplexing means and the frequency shift modulation signal or phase shift modulation signal;
Of the signals output from the optical receiving means, the difference between the center frequency of the optical time division multiplexed signal and the center frequency of the optical signal output from the optical output means is shifted by 1/2 of the signal speed of the optical time division multiplexed signal. Transmitting means for transmitting a signal of electrical frequency,
Comprising intensity detection means for intensity detection of the output of the transmission means,
Based on the difference between the center frequency of the optical time division multiplexed signal transmitted by the transmission means and the center frequency of the optical signal output by the optical output means, the signal speed of the optical time division multiplexed signal is 1 by the output of the intensity detection means. A clock phase synchronization circuit, wherein the phase of the output signal of the signal generating means is controlled so that a signal having an electrical frequency shifted by / 2 is maximized.   3. The clock phase synchronization circuit according to claim 1, wherein the optical receiving means includes a differential reception type optical detector. In an optical receiver for demultiplexing and receiving optical time division multiplexed signals,
Signal generating means for generating a signal synchronized in phase with the optical receiver;
An optical signal output means for outputting an optical signal subjected to frequency shift keying or phase shift keying by the output of the signal generating means;
Optical multiplexing means for multiplexing the optical time division multiplexed signal and the frequency shift keying signal or phase shift keying signal output from the optical signal output means;
Optical receiving means for optical heterodyne reception of the optical time division multiplexed signal combined with the optical multiplexing means and the frequency shift modulation signal or phase shift modulation signal;
First transmission means for transmitting a signal having a frequency corresponding to a signal to be demultiplexed among the intermediate frequency signals output from the optical reception means;
Demodulation means for demodulating the output of the first transmission means;
1/2 from the difference between the center frequency of the optical signal output from the central frequency and the optical signal output means of the optical time division multiplex signal out of the signal output from the light receiving means of the signal speed of the optical time division multiplex signal A second transmission means for transmitting a signal having an electrical frequency shifted by
Comprising intensity detecting means for intensity detecting the output of the second transmitting means,
The optical time division multiplex signal is obtained from the difference between the center frequency of the optical time division multiplex signal transmitted by the second transmission means and the center frequency of the optical signal output from the optical signal output means by the output of the intensity detection means. An optical receiver characterized in that the phase of the output signal of the signal generating means is controlled so that a signal with an electrical frequency shifted by ½ of the signal speed is maximized. In an optical receiver for demultiplexing and receiving optical time division multiplexed signals,
Signal generating means for generating a signal synchronized in phase with the optical receiver;
An optical signal output means for outputting an optical signal subjected to frequency shift keying or phase shift keying by the output of the signal generating means;
Optical multiplexing means for multiplexing the optical time division multiplexed signal and the frequency shift keying signal or phase shift keying signal output from the optical signal output means;
First optical receiving means for optical heterodyne reception of the optical time division multiplexed signal combined with the optical multiplexing means and a part of the frequency shift keying signal or phase shift keying signal;
First transmission means for transmitting a signal having a frequency corresponding to a signal to be demultiplexed among the intermediate frequency signals output from the first optical reception means;
Demodulation means for demodulating the output of the first transmission means;
Second optical receiving means for optically heterodyne receiving a part of the optical time division multiplexed signal combined with the optical multiplexing means and the frequency shift keying signal or phase shift keying signal;
From the difference between the center frequency of the optical signal output from the central frequency and the optical signal output means of the optical time division multiplex signal of the signal output from the second light receiving means of the signal speed of the optical time division multiplex signal A second transmission means for transmitting a signal having an electrical frequency shifted by ½,
Comprising intensity detecting means for intensity detecting the output of the second transmitting means,
The optical time division multiplex signal is obtained from the difference between the center frequency of the optical time division multiplex signal transmitted by the second transmission means and the center frequency of the optical signal output from the optical signal output means by the output of the intensity detection means. An optical receiver characterized in that the phase of the output signal of the signal generating means is controlled so that a signal with an electrical frequency shifted by ½ of the signal speed is maximized. In an optical receiver for demultiplexing and receiving optical time division multiplexed signals,
First optical branching means for branching the optical time division multiplexed signal;
Signal generating means for generating a signal synchronized in phase with the optical receiver;
An optical signal output means for outputting an optical signal subjected to frequency shift keying or phase shift keying by the output of the signal generating means;
Second optical branching means for branching the output optical signal of the optical signal output means;
At least one optical delay means for providing an optical delay to the output optical signal of the second optical branching means;
First optical coupling means for combining the output optical signal of the second optical branching means and the output optical signal of the first optical branching means;
Provided corresponding to the optical delay means, and at least one second optical coupling means for multiplexing the output optical signal of the optical delay means and the output optical signal of the first optical branching means;
A plurality of optical receiving means provided corresponding to the first and second optical coupling means, for optically heterodyne-receiving the output optical signal combined by the first and second optical coupling means;
A plurality of demodulation means that are provided corresponding to the plurality of optical receiving means and demodulate using a signal of a frequency corresponding to a signal to be demultiplexed among the intermediate frequency signals output from the optical receiving means;
Is connected to one of said plurality of light receiving means, the center frequency of the optical signal output from the central frequency and the optical signal output means of the optical time division multiplex signal of the signal output from the light receiving means Phase control signal extraction means for extracting a phase control signal using a signal having an electrical frequency shifted from the difference by 1/2 of the signal speed of the optical time division multiplexed signal,
Due to the phase control signal output from the phase control signal extraction means, the signal speed of the optical time division multiplexed signal is calculated from the difference between the center frequency of the optical time division multiplexed signal and the center frequency of the optical signal output from the optical signal output means. The phase of the output signal of the signal generating means is controlled so that the signal of the electrical frequency shifted by ½ is maximized. 7. The optical receiver according to claim 4 , wherein the optical receiving means includes a differential reception type optical detector. 6. The optical receiver according to claim 5, wherein the first and second optical receiving means include a differential reception type optical detector.

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