JP4864822B2 - Optical receiver - Google Patents

Description

  The present invention relates to an optical receiver that demultiplexes and receives 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 (Non-Patent Document 1).

  As shown in FIG. 1, a conventional optical receiver 101 phase-modulates a signal generator 102 and an optical time division multiplexed signal input from an optical signal input unit of the optical receiver 101 by the output of the signal generator 102. A phase modulator 103; an optical bandpass filter 104 that transmits only a target signal channel component of the output of the phase modulator 103; an optical amplifier 105 that amplifies the signal; and an optical detection that photoelectrically converts the output of the optical amplifier 105 And a demodulator 107 that demodulates the output of the optical detector 106 and outputs a target signal.

Here, FIG. 2 shows the relationship between the time waveform of the signal and the frequency component (hereinafter, spectrum) in (a), (b), (c), and (d) in FIG. 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. 2, and the signal channels α, β, γ, and δ are multiplexed. At this time, the spectrum of the optical time division multiplexed signal spreads from the center frequency f _s by the modulation speed f _B. Further, by the signal generator 102 and the phase modulator 103, as shown in (b) of FIG. 2, the rising edge of the phase modulation overlaps with the target signal channel α at a rate of 1/4 of the modulation rate f _B. By phase-modulating the optical time division signal, the frequency variation occurs simultaneously with the phase variation in the optical time division multiplexed signal. As a result, an optical signal in which the target signal channel α is shifted to the high frequency side by Δf as shown in FIG. 2C is output. By transmitting only the spectrum corresponding to the signal channel α out of the spectrum of the optical signal using the optical bandpass filter 104, only the target signal channel α is demultiplexed as shown in FIG. The demultiplexed signal can be demodulated using the optical amplifier 105, the optical detector 106, and the demodulator 107.
Koji Igarashi, Kazuhiro Kato, Kazuo Kikuchi, “Optical Receiver for 160 Gbit / s OTDM Based on Signal Processing in the Optical Frequency Domain”, Society of Information and Communication Society Society B-10-65 (2006), September 2006 May 22, p259.

  Since the conventional optical receiver shown in FIG. 1 demultiplexes the optical time division multiplexed signal in the optical domain, it can demultiplex the optical time division multiplexed signal at a higher speed than the case of demultiplexing in the electrical domain. It becomes possible. However, since this method uses many relatively expensive optical components, it is difficult to construct an optical receiver economically.

  The present invention has been made in view of such problems, and an object of the present invention is to perform demultiplexing at the time of receiving an optical time division multiplexed signal in an expensive optical component such as an optical amplifier or a phase modulator. An object of the present invention is to provide an optical receiver which can be realized by an economical configuration with a reduced number.

According to a first aspect of the present invention, in an optical receiver for demultiplexing and receiving an optical time division multiplexed signal, a signal generator and an optical signal directly frequency shift modulated by the output of the signal generator are output at a constant intensity. A direct modulation light source, an optical coupler for multiplexing the optical time division multiplexed signal and a direct frequency shift keying signal output from the direct modulation light source, and an optical time division multiplexing multiplexed by the optical coupler. An optical detector for receiving an optical heterodyne signal and a direct frequency shift keying signal and outputting an intermediate frequency signal; and transmitting an intermediate frequency signal corresponding to a target signal among the intermediate frequency signals output from the optical detector. And an intermediate frequency signal demodulator that demodulates the signal demultiplexed by the electric bandpass filter and outputs the target signal .
As a result, only the target signal channel of the optical time division multiplexed signal transmitted at high speed can be received by optical heterodyne reception using frequency shift modulated light as local oscillation light. It is possible to perform demultiplexing without using an optical receiver having an expensive and complicated configuration.

According to a second aspect of the present invention, in an optical receiver for demultiplexing and receiving an optical time division multiplexed signal, a light source that outputs continuous light, a signal generator, and an output of the signal generator are output from the light source. An external modulator for performing frequency shift keying or phase shift keying on the continuous light with constant intensity, the optical time division multiplexed signal, and the frequency shift keying signal or phase shift keying signal output from the external modulator. An optical coupler for multiplexing, an optical detector for optically heterodyne receiving an optical time division multiplexed signal and a frequency shift keying signal or a phase shift keying signal combined by the optical coupler, and outputting an intermediate frequency signal ; , an electrical band-pass filter for demultiplexing transmitted through the intermediate frequency signal corresponding to the desired signal in the intermediate frequency signal output from the optical detector, a signal demultiplexing by the electrical bandpass filter recovery Characterized in that to and an intermediate frequency signal demodulator for outputting a signal of the object.
As a result, only the target signal channel of the optical time division multiplexed signal transmitted at high speed can be optically heterodyne received by optical heterodyne reception using frequency shift keyed light or phase shift keyed light as local oscillation light. Therefore, demultiplexing can be performed without using an expensive and complicated optical receiver including an optical amplifier.

According to a third aspect of the present invention, in the optical receiver of the first or second aspect, a differential reception type optical detector is used as the optical detector.
As a result, in the optical receiver 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 detection is performed, and the optical receiver having higher reception characteristics. Can be configured.

According to a fourth aspect of the present invention, there is provided an optical receiver for demultiplexing and receiving an optical time division multiplexed signal, a first optical branching device for branching the optical time division multiplexed signal, a signal generator, and the signal generator. A modulated light source that outputs an optical signal that has been frequency-shift-modulated or phase-shift-modulated by the output of the output, a second optical splitter that branches the output optical signal of the modulated light source, and an output of the second optical splitter A first optical coupler that multiplexes at least one optical delay unit that adds an optical delay to the optical signal, an output optical signal of the second optical splitter, and an output optical signal of the first optical splitter; And at least one second optical coupler that is provided corresponding to the optical delay unit and multiplexes the output optical signal of the optical delay unit and the output optical signal of the first optical branching unit, It provided corresponding to said first and second optical coupler, the first and second optical coupler A plurality of optical detectors to output an intermediate frequency signal multiplexed output optical signal optical heterodyne receiver, said plurality of provided corresponding to the light detector, an intermediate frequency signal outputted from the optical detector A plurality of electrical bandpass filters that transmit and demultiplex an intermediate frequency signal corresponding to a target signal, and a signal that is provided corresponding to the plurality of electrical bandpass filters and demultiplexed by the electrical bandpass filter And a plurality of intermediate frequency signal demodulators for outputting the target signal .
Thereby, a plurality of signal channels can be demultiplexed and received simultaneously.

According to a fifth aspect of the present invention, in the optical receiver of the fourth aspect, a differential reception type optical detector is used as the optical detector.
As a result, in the optical receiver of the fourth aspect, it becomes possible to remove the baseband component of the optical time division multiplexed signal generated when optical heterodyne detection is performed, and an optical receiver with higher reception characteristics is configured. It becomes possible.

  The present invention performs high-speed signal demultiplexing by performing optical heterodyne reception using frequency shift keyed light or phase shift keyed light as local oscillation light when receiving optical time division multiplexed signals. As a result, it is possible to realize a demultiplexing receiver with an economical configuration.

Embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 3 is a diagram showing the configuration of the optical receiver according to the first embodiment of the present invention. As shown in FIG. 3, the optical receiver 201 according to the first embodiment includes a signal generator 202 and a direct modulation light source 203 that outputs an optical signal that is directly frequency shift modulated by the output of the signal generator 202. And an optical coupler 204 that combines the optical time division multiplexed signal input from the optical signal input unit of the optical receiver 201 and the optical signal output from the direct modulation light source 203, and the optical coupler 204 An optical detector 205 for optical heterodyne reception of the optical time-division multiplexed signal and the optical signal output from the direct modulation light source 203, an electrical bandpass filter 206 that transmits a part of the band of the output signal of the optical detector 205, An intermediate frequency signal demodulator 207 that demodulates the output of the electric bandpass filter 206 and outputs a target signal is provided.

  At this time, the signal generator 202 can be configured using, for example, an oscillator and an electric amplifier, and the intermediate frequency signal demodulator 207 can be configured using, for example, an envelope detector and an electric low-pass filter. It is.

Here, FIG. 4 shows an example of the relationship between the time waveform of the signal and the spectrum at (a), (b), (c), and (d) in FIG. The time waveform of the optical time division multiplexed signal input from the optical signal input unit of the optical receiver 201 is (a) in FIG. 4, and the signal channels α, β, γ, and δ are multiplexed. At this time, the spectrum of the optical time division multiplexed signal spreads from the center frequency f _s by the modulation speed f _B. Further, by the signal generator 202 and the direct modulation light source 203, as shown in FIG. 4B, the frequency is -Δf to + Δf at a center frequency f _{LO, a} constant intensity, and a quarter of the modulation speed f _B. Fluctuating local oscillation light is output. Next, the optical time division multiplexed signal and the local oscillation light are combined using the optical coupler 204. At this time, the peak of the target signal channel α of the optical time division multiplexed signal and the frequency fluctuation of the local oscillation light are + Δf. It combines so that it may become the timing which becomes. Thereafter, output from the optical detector 205 causes optical heterodyne reception, and the target signal channel α is shifted from the center frequency f _s −f _LO to the lower frequency side by Δf as shown in FIG. The intermediate frequency signal is output. By passing only the spectrum corresponding to the signal channel α out of the spectrum of the intermediate frequency signal using the electric bandpass filter 206, only the target signal channel α is demultiplexed as shown in FIG. The target signal channel α can be demodulated by demodulating the demultiplexed signal using the intermediate frequency signal demodulator 207.

  When a signal channel other than the signal channel α is received in the above-described configuration, the optical coupler 204 matches the timing of the frequency fluctuation of the local oscillation light source to + Δf with the peak of the target signal channel. Just wave.

In the embodiment shown in FIG. 4, the signal band γ is received by transmitting the spectrum shifted by Δf from the center frequency f _s −f _LO of the intermediate frequency signal to the high frequency side in the electric bandpass filter 206. In addition, an arbitrary signal channel can be received by multiplexing with the optical coupler 204 so that the timing at which the frequency fluctuation of the local oscillation light source becomes −Δf coincides with the peak of the target signal channel. can do.

At this time, the intermediate frequency signal output from the electric band pass filter 206 can be used as a radio signal. FIG. 4 shows a case where the center frequency f _s of the optical time division multiplexed signal is higher than f _LO, but conversely when the center frequency f _s of the optical time division multiplexed signal is lower than f _LO. Similarly, it goes without saying that a signal demultiplexing operation can be realized.

  By adopting the configuration as in the first embodiment, it is possible to realize the demultiplexing operation of the optical time division multiplexed signal transmitted at a high speed by using components having a relatively low frequency compared with the signal speed. Become. In addition, since photoelectric conversion is performed using optical heterodyne reception, signals can be amplified and received, and it is not necessary to use an optical amplifier required in the prior art shown in FIG. Furthermore, since demultiplexing is performed by using more economical electrical components than optical components, it is not necessary to perform signal processing in the optical frequency domain, and an economical receiver can be configured.

(Second Embodiment)
FIG. 5 is a diagram showing a configuration of an optical receiver according to the second embodiment of the present invention. As illustrated in FIG. 5, the optical receiver 301 according to the second embodiment includes a light source 302 that outputs continuous light, a signal generator 303, and a continuous output output from the light source 302 based on the output of the signal generator 303. An external modulator 304 that performs frequency shift keying or phase shift keying of light, an optical time division multiplexed signal that is input from the optical signal input unit of the optical receiver 301, and a frequency shift keyed signal that is output from the external modulator 304 Alternatively, an optical coupler 305 that multiplexes the phase shift keying signal, and an optical detection that optically heterodyne receives the optical time division multiplexed signal and the frequency shift keying signal or the phase shift keying signal combined by the optical coupler 305. 306, an electric bandpass filter 307 that transmits a part of the band of the output signal of the optical detector 306, and an intermediate frequency signal that demodulates the output of the electric bandpass filter 307 and outputs a target signal. They comprise a demodulator 308.

At this time, the signal generator 303 can be configured using, for example, an oscillator and an electric amplifier, and the intermediate frequency signal demodulator 308 can be configured using, for example, an envelope detector and an electric low-pass filter. It is.
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, it is possible to realize the demultiplexing operation of the optical time division multiplexed signal transmitted at a high speed by using a component having a relatively low frequency compared with the signal speed. Become. Furthermore, since demultiplexing is performed by using more economical electrical components than optical components, it is not necessary to perform signal processing in the optical frequency domain, and an economical receiver 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. Multiple demultiplexing operations can be realized.

(Third embodiment)
FIG. 6 is a diagram illustrating a configuration of an optical receiver according to the third embodiment of the present invention. As shown in FIG. 6, an optical receiver 401 according to the third embodiment includes a signal generator 402 and a direct modulation light source 403 that outputs an optical signal that is directly frequency shift modulated by the output of the signal generator 402. And an optical coupler 404 that combines the optical time division multiplexed signal input from the optical signal input unit of the optical receiver 401 and the optical signal output from the direct modulation light source 403, and the optical coupler 404 A differential reception optical detector 405 for optical heterodyne reception of the optical time division multiplexed signal and the optical signal output from the direct modulation light source 203, and a part of the band of the output signal of the differential reception optical detector 405 is transmitted. And an intermediate frequency signal demodulator 407 that demodulates the output of the electric bandpass filter 406 and outputs a target signal.

At this time, the signal generator 402 can be configured using, for example, an oscillator and an electric amplifier, and the intermediate frequency signal demodulator 407 can be configured using, for example, an envelope detector and an electric low-pass filter. It is.
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 demultiplexing operation of the optical time division multiplexed signal transmitted at a high speed by using a component having a relatively low frequency compared with the signal speed. Become. Furthermore, since demultiplexing is performed by using more economical electrical components than optical components, it is not necessary to perform signal processing in the optical frequency domain, and an economical receiver can be configured. Further, by using a differential reception type optical detector at the time of optical heterodyne reception (at the time of photoelectric conversion), there is no coupling loss that occurs when signals are combined in the optical coupler 404, and the optical time division multiplexed signal Since the reception component is directly canceled, the reception characteristics can be greatly improved, and the intermediate frequency signal generated after the optical detection can be shifted to the lower frequency side, thereby reducing the desired band of the optical detector and electrical components. Can contribute to an economical receiver configuration.

(Fourth embodiment)
FIG. 7 is a diagram showing a configuration of an optical receiver according to the fourth embodiment of the present invention. As shown in FIG. 7, an optical receiver 501 according to the fourth embodiment includes an optical branching device 502 that branches an optical time division multiplexed signal input from an optical signal input unit of the optical receiver 501, and a signal generator A modulator 503, a modulation light source 504 that outputs an optical signal that is frequency-shift-modulated or phase-shift-modulated using the output of the signal generator 503, an optical splitter 505 that branches the output optical signal of the modulation light source 504, A plurality of optical delay units 506-2 to 506-4 that add an optical delay to the output optical signal of the optical branching unit 505, and light that combines the output optical signal of the optical branching unit 502 and the output optical signal of the optical branching unit 505 A coupler 507-1, optical couplers 507-2 to 507-4 for combining the output optical signal of the optical branching device 502 and the output optical signals of the optical delay units 506-2 to 506-4, and optical Receive the outputs of couplers 507-1 to 507-4 and An optical receiver 508-1～508-4 for demodulating a.

  At this time, the signal generator 503 can be configured using, for example, an oscillator and an electric amplifier, and the modulated light source 504 is a direct modulation light source or a continuous light source as in the first to third embodiments. The optical receivers 508-1 to 508-4 can be configured by using an external modulator, and the optical receivers 508-1 to 508-4 are configured with an optical detector, an electric bandpass filter, an intermediate frequency, as in the first to third embodiments. A signal demodulator or a differential reception type optical detector, an electric bandpass filter, and an intermediate frequency demodulator can be used.

At this time, the basic operation principle is the same as that of the first embodiment.
When receiving an optical signal, the signal is branched to a plurality of receiving units, and the timing of the frequency fluctuation of the local oscillation light is made to coincide with the signal channel to be received using the optical delay units 506-2 to 506-4. A plurality of signal channels can be received simultaneously.

  As described above, according to the present invention, the number of expensive optical components such as optical amplifiers and phase modulators can be reduced by using both optical domain and electrical domain signal processing for demultiplexing when receiving optical time division multiplexed signals. Can be realized with an economical configuration.

It is a figure which shows the structure of the conventional optical receiver. It is a figure which shows the time waveform and spectrum of the signal processed inside the conventional optical receiver. It is a figure which shows the structure of the optical receiver which concerns on the 1st Embodiment of this invention. It is a figure which shows the time waveform and spectrum of the signal processed inside the optical receiver which concerns on 1st Embodiment. It is a figure which shows the structure of the optical receiver which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structure of the optical receiver which concerns on the 3rd Embodiment of this invention. It is a figure which shows the structure of the optical receiver which concerns on the 4th Embodiment of this invention.

Explanation of symbols

101, 201, 301, 401, 501 Optical receiver 102, 202, 303, 402, 503 Signal generator 103 Phase modulator 104 Optical bandpass filter 105 Optical amplifier 106, 205, 306 Optical detector 107 Demodulator 203, 403 Direct modulation light source 204,305,404,507-1 to 507-4 Optical coupler 206,307,406 Electric band pass filter 207,308,407 Intermediate frequency signal demodulator 302 Continuous light source 304 External modulator 405 Differential reception type Optical detectors 502 and 505 Optical splitter 504 Modulated light source 506-2 to 506-4 Optical delay device 508-1 to 508-4 Optical receiver

Claims (5)

In an optical receiver for demultiplexing and receiving optical time division multiplexed signals,
A signal generator;
A direct modulation light source that outputs an optical signal that is directly frequency shift modulated by the output of the signal generator at a constant intensity;
An optical coupler for combining the optical time division multiplexed signal and the direct frequency shift keying signal output from the direct modulation light source;
An optical detector that optically heterodyne-receives an optical time division multiplexed signal and a direct frequency shift keying signal combined by the optical coupler and outputs an intermediate frequency signal ;
An electrical bandpass filter that transmits and demultiplexes an intermediate frequency signal corresponding to a target signal among the intermediate frequency signals output from the optical detector;
An intermediate frequency signal demodulator that demodulates the signal demultiplexed by the electric bandpass filter and outputs the target signal;
An optical receiver comprising: In an optical receiver for demultiplexing and receiving optical time division multiplexed signals,
A light source that outputs continuous light;
A signal generator;
An external modulator that performs frequency shift modulation or phase shift modulation of the continuous light output from the light source at a constant intensity by the output of the signal generator;
An optical coupler for combining the optical time division multiplexed signal and the frequency shift keying signal or phase shift keying signal output from the external modulator ;
An optical detector that optically heterodyne-receives an optical time division multiplexed signal combined with the optical coupler and a frequency shift modulation signal or a phase shift modulation signal and outputs an intermediate frequency signal ;
An electrical bandpass filter that transmits and demultiplexes an intermediate frequency signal corresponding to a target signal among the intermediate frequency signals output from the optical detector;
An intermediate frequency signal demodulator that demodulates the signal demultiplexed by the electric bandpass filter and outputs the target signal;
An optical receiver comprising: The optical receiver according to claim 1 or 2,
A differential receiver type optical detector is used as the optical detector. In an optical receiver for demultiplexing and receiving optical time division multiplexed signals,
A first optical branching device for branching the optical time division multiplexed signal;
A signal generator;
A modulated light source that outputs an optical signal that is frequency-shift modulated or phase-shift modulated by the output of the signal generator;
A second optical branching device for branching the output optical signal of the modulated light source;
At least one optical delay unit that provides an optical delay to the output optical signal of the second optical branching unit;
A first optical coupler that combines the output optical signal of the second optical splitter and the output optical signal of the first optical splitter;
At least one second optical coupler that is provided corresponding to the optical delayer and multiplexes the output optical signal of the optical delayer and the output optical signal of the first optical splitter;
A plurality of lights provided corresponding to the first and second optical couplers and receiving an optical heterodyne of the output optical signal combined by the first and second optical couplers and outputting an intermediate frequency signal A detector,
A plurality of electrical bandpass filters that are provided corresponding to the plurality of optical detectors and transmit and demultiplex an intermediate frequency signal corresponding to a target signal among the intermediate frequency signals output from the optical detector;
A plurality of intermediate frequency signal demodulators that are provided corresponding to the plurality of electrical bandpass filters, demodulate signals demultiplexed by the electrical bandpass filters, and output the target signal;
An optical receiver comprising: The optical receiver according to claim 4.
A differential receiver type optical detector is used as the optical detector.

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