JP2001168845A - Optical demultiplexer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical demultiplexer where the number of components can be decreased, power consumption is reduced and the size is reduced, because it is not required to receive an optical clock signal externally and the optical adjustment can be facilitated because it is not required to adjust the polarized state of demultiplexed optical signals. SOLUTION: A three-port optical circulator 132 transmits an optical multiplex pulse stream 141, resulting from applying optical time division multiplex(OTDM) to optical pulse streams of N channels to a hybrid mode synchronization DBR semiconductor laser 1 and a self-oscillating optical pulse stream whose frequency is 1/N of the pulse repeating frequency of the optical multiplex pulse stream 141 generated by the hybrid mode synchronization DBR semiconductor laser 1, the optical multiplex pulse stream 141, and an optically combined light consisting of a four-wave mixed light generated by the interaction between the self-oscillating optical pulse streams and the optical multiplex pulse stream 141 are delivered to a wavelength filter 133. The wavelength filter 133 outputs only the four-wave mixed light from the composite light as a specific channel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical multiplexing / demultiplexing apparatus used on the receiving side of long-distance optical fiber communication.

[0002]

2. Description of the Related Art An optical time division multiplexing (OTDM) transmission system is an example of a transmission system for realizing large-capacity long-distance optical fiber communication. In this transmission method, an optical pulse train of a low bit rate (for example, about 10 Gbit / S) within an electrically controllable range is generated, and this optical pulse train is multiplexed on a plurality of channels on a time axis to increase a transmission capacity. I have. For example, 16 channels are multiplexed to increase to about 160 Gbit / S. On the receiving side, it is necessary to separate the multiplexed optical pulse train for each channel. Therefore, an optical multiplexing / demultiplexing device is required. As such an optical multiplexing / demultiplexing device, a plurality of optical multiplexing / demultiplexing devices using an all-optical method of controlling light with light have been reported. One example is S. Kawanish
i, T.Morioka, O.Kamatani, H.Takara, JMJacob and M.Sa
ruwatari, ELECTRONICS LETTERS 9th June 1994 Vol.30
No. 12 (cited reference 1).

[0003]

However, the above-mentioned prior art has the following problems to be solved. In addition to the technology disclosed in the above document, the technology disclosed in a plurality of other documents also has a common point in an optical multiplexing / demultiplexing device using an all-optical method of controlling light with light. An optical clock signal for generating an optical pulse train is required separately. Further, it is necessary to adjust the polarization state of both the optical clock signal and the multiplexed optical signal. In order to satisfy such demands, optical multiplexing / demultiplexing devices have necessarily been large and expensive. Also, there remains a problem to be solved in that optical adjustment becomes complicated.

[0004]

The present invention employs the following structure to solve the above problems. <Structure 1> An N-channel optical pulse train is optically time-division multiplexed (O
TDM) received optical multiplexed pulse train from the first port and sends it out to the mode-locked DBR semiconductor laser through the second port, and the self-oscillating optical pulse train generated by the mode-locked DBR semiconductor laser; An optical circulator for receiving a composite light composed of four-wave mixing light generated by an interaction between the self-oscillating optical pulse train and the optical multiplexed pulse train from the second port and outputting the composite light to a third port; An optical wavelength filter that receives the optical composite light from the third port and outputs only the four-wave mixing light, and the mode-locked DB
The R semiconductor laser generates a self-oscillating optical pulse train at a frequency of 1 / N of the pulse repetition frequency of the optical multiplexing pulse train, and the timing at which the self-oscillating optical pulse train is generated coincides with any channel of the optical multiplexing pulse train. An optical multiplexing / demultiplexing apparatus characterized in that the wavelength of the self-oscillating optical pulse train is different from the wavelength of the optical multiplexing pulse train.

<Structure 2> In the optical multiplexing / demultiplexing device according to Structure 1, the mode-locked DBR semiconductor laser is
A saturable absorption region for synchronizing the self-oscillation light pulse train with an externally applied AC voltage source, and a DBR region including a diffraction grating that matches the wavelength of the self-oscillation light pulse train are arranged. An AC voltage source of 1 / N of the pulse repetition frequency of the optical multiplex pulse train is applied,
An optical demultiplexing device, wherein a part of the self-oscillating light pulse train synchronized with the AC voltage source is reflected by the DBR region.

<Structure 3> In the optical multiplexing / demultiplexing device according to Structure 1 or 2, an optical delay circuit for delaying a timing at which the optical multiplexed pulse train is input to the mode-locked DBR semiconductor laser; An optical detector that receives a part of the four-wave mixing light output from the semiconductor laser and detects the light intensity thereof; and a controller that controls a delay time of the optical delay circuit, wherein the controller detects a detection result of the optical detector. An optical multiplexing / demultiplexing device for controlling the delay time of the optical delay circuit based on the above-mentioned factor to maintain the light intensity of the four-wave mixing light at a predetermined level or more.

<Structure 4> In the optical multiplexing / demultiplexing device according to Structure 1 or 2, an electric delay circuit for delaying a timing at which the AC voltage source is applied to the saturable absorption region, and the mode-locked DBR semiconductor An optical detector for receiving a part of the four-wave mixing light output by the laser and detecting the light intensity thereof, and a control circuit for controlling a delay time of the electric delay circuit, wherein the control circuit detects the optical detector. An optical multiplexing / demultiplexing device, wherein the delay time of the electric delay circuit is controlled based on the result to maintain the light intensity of the four-wave mixing light at a predetermined level or more.

<Structure 5> An optical isolator for inputting an optical signal for receiving an optical multiplexed pulse train in which an N-channel optical pulse train has been subjected to optical time division multiplexing (OTDM) and sending it to a mode-locked DBR semiconductor laser, and the mode-locked DBR semiconductor laser Generates a self-oscillating light pulse train, an optical multiplexed pulse train, and an optical composite light composed of four-wave mixing light generated by the interaction of the self-oscillating light pulse train and the optical multiplexed pulse train from the mode-locked DBR semiconductor laser. An optical isolator for receiving and sending out to the optical wavelength filter for extracting four-wave mixed light, and an optical wavelength filter for receiving the optical composite light from the optical isolator for extracting four-wave mixed light and outputting only the four-wave mixed light, The above mode synchronization DB
The R semiconductor laser self-oscillates at a frequency of 1 / N of the pulse repetition frequency of the optical multiplex pulse train, and the timing at which this self-oscillation optical pulse train is generated coincides with any channel of the optical multiplex pulse train. An optical multiplexing / demultiplexing device, wherein the wavelength of the oscillation light pulse train is different from the wavelength of the optical multiplexing pulse train.

<Structure 6> In the optical demultiplexer according to Structure 5, the mode-locked DBR semiconductor laser is
A saturable absorption region that synchronizes the self-oscillation light pulse train with an externally applied AC voltage source at the center of the internal light path, and a diffraction grating that matches the wavelength of the self-oscillation light pulse train at both ends of the light passage. A DBR region is provided, and an AC voltage source of 1 / N of the pulse repetition frequency of the optical multiplex pulse train is applied to the saturable absorption region, and a part of the self-oscillating light pulse train synchronized with this AC voltage source is DB
An optical demultiplexer, which is reflected between R regions.

<Structure 7> In the optical multiplexing / demultiplexing device according to Structure 5 or 6, an optical delay circuit for delaying a timing at which the optical multiplexed pulse train is input to the mode-locked DBR semiconductor laser; An optical detector that receives a part of the four-wave mixing light output from the semiconductor laser and detects the light intensity thereof; and a controller that controls a delay time of the optical delay circuit, wherein the controller detects a detection result of the optical detector. An optical multiplexing / demultiplexing device for controlling the delay time of the optical delay circuit based on the above-mentioned factor to maintain the light intensity of the four-wave mixing light at a predetermined level or more.

<Structure 8> In the optical multiplexing / demultiplexing device according to Structure 5 or 6, an electric delay circuit for delaying a timing at which the AC voltage source is applied to the saturable absorption region, and the mode-locked DBR semiconductor An optical detector for receiving a part of the four-wave mixing light output by the laser and detecting the light intensity thereof, and a control circuit for controlling a delay time of the electric delay circuit, wherein the control circuit detects the optical detector. An optical multiplexing / demultiplexing device, wherein the delay time of the electric delay circuit is controlled based on the result to maintain the light intensity of the four-wave mixing light at a predetermined level or more.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below using specific examples. <Structure of Concrete Example 1> FIG.
As shown in FIG. 1, the optical multiplexing / demultiplexing apparatus of the first embodiment includes a hybrid mode-locked DBR (Distributed Bragg Reflector) semiconductor laser 1, a coupling lens 131, a three-port optical circulator 132, and a wavelength filter 133.

A hybrid mode synchronous DBR (Distribute
The ted Bragg Reflector semiconductor laser 1 is a synchronous mode laser that oscillates and outputs an optical pulse train having a pulse repetition frequency fml. For details of the hybrid mode-locked DBR semiconductor laser 1, see "S. Arahira and Y. Ogawa, Passive an
d hybrid modelockings in multi-electrode DBR laser
with two gain sections ELECTRONICS LETTERS 11th M
ay 1995 Vol. 31 No. 10 pp. 808-809 "(cited reference 2). Coupling lens 1
An optical lens 31 couples an optical path between the three-port optical circulator 132 and the hybrid mode-locked DBR semiconductor laser 1.

The three-port optical circulator 132 has three input / output ports, outputs an optical signal received from the first port to a second port, and outputs an optical signal received from the second port to a third port. The circulator outputs the optical signal received from the third port to the first port. Here, an optical multiplexed signal pulse train in which an N-channel optical pulse train is subjected to optical time division multiplexing (OTDM) is received from a first port and passed through a second port.
The hybrid mode-locked DBR semiconductor laser 1 transmits the self-oscillating optical pulse train, the optical multiplexed signal pulse train, the self-oscillating optical pulse train, and the optical multiplexed pulse train output from the hybrid mode-locked DBR semiconductor laser 1 via The composite light composed of the four-wave mixing light generated by the interaction is received from the second port and output to the wavelength filter 133 via the third port.

The wavelength filter 133 outputs a composite light composed of the self-oscillation light pulse train output from the hybrid mode-locked DBR semiconductor laser 1 from the third port of the optical circulator 132, the light multiplexed signal pulse train, and four-wave mixing light. This is a filter that receives and outputs only four-wave mixing light. Here, the four-wave mixed light means a nonlinear optical medium,
Two photons at angular frequency ω1 and one photon at angular frequency ω2 disappear, and one photon with a new wavelength at angular frequency 2ω1-ω2 is generated instead. This photon is called four-wave mixed light.
If applied to the present invention, the photon of angular frequency ω1 is a self-oscillation light pulse train of the hybrid mode-locked DBR semiconductor laser 1, and the photon of angular frequency ω2 is an optical multiplex pulse train. The wavelength-converted light generated by the interaction between the self-oscillation light pulse train and the optical multiplex pulse train is four-wave mixing light (described again using an experimental example later).

Further, the hybrid mode-locked DBR semiconductor laser 1 has a saturable absorption region 101 and a gain region 10.
2, the passive waveguide region 103, and the DBR (Distributed
Bragg reflector) region 104 and n-type common electrode 111
A saturable absorber p-side electrode 112, a gain region p-side electrode 113, a passive waveguide p-side electrode 114, a DBRp-side electrode 115, a saturable absorber reverse bias voltage source 121,
A gain region current source 122, a passive waveguide current or reverse bias voltage source 123, a DBR current or reverse bias voltage source 124, and an AC voltage source 125 are provided.

The saturable absorption region 101 is a portion that causes mode locking. In this region, an AC voltage source 125 is applied via the saturable absorber p-side electrode 112 and the n-type common electrode 111, and the self-oscillation light is synchronized with the AC voltage source 125. The gain region 102 is a portion that generates light. In this region, the gain region p-side electrode 1
13 and the gain region current source 12 via the n-type common electrode 111.
A region 2 is applied to excite carriers to cause oscillation.

The passive waveguide region 103 is a waveguide that is transparent to the oscillation wavelength. In this area, a passive waveguide current or a reverse bias voltage source 123 is applied via a passive waveguide p-side electrode 114 and an n-type common electrode 111. DBR
A DBR current or a reverse bias voltage source 124 is applied to the region 104 via a DBRp side electrode 115 and an n-type common electrode 111. Further, it is a region provided with a DBR (Distributed Bragg Reflector) for determining an oscillation wavelength and an oscillation wavelength width, that is, a diffraction grating.

The present invention is established based on two basic principles. The basic principle will be described below. Basic Principle 1 “The frequency f near the frequency fm
By applying an AC voltage source 125 of rf, a stable optical pulse train synchronized with the AC voltage source 125 can be generated from the hybrid mode-locked DBR semiconductor laser 1 ". In FIG. When the multiple pulse train 141 is not input, the current source or the reverse bias voltage sources 121 to 12
When a predetermined bias is applied to 4, the hybrid mode-locked DBR semiconductor laser 1 starts oscillating. Frequency fml that coincides with the orbital frequency of the laser or its integral multiple
An optical pulse train with a nearby pulse repetition frequency is output.

At this time, the frequency fm is applied to the saturable absorption region 101.
When an AC voltage source having a frequency frf near 1 is applied, the hybrid mode-locked DBR semiconductor laser 1 generates a stable optical pulse train with little jitter at a pulse repetition frequency frf. The details are disclosed in the above cited reference 2.

Basic Principle 2 When the hybrid mode-locked DBR semiconductor laser 1 generates self-oscillation light of wavelength λs and injects injection light of wavelength λb from outside, the self-oscillation light of wavelength λs and wavelength Not only the injected light of λb but also the wavelength-converted light (four-wave mixed light) having the wavelength λt is output. ”A part of this phenomenon is disclosed in the above cited reference 1, but here, the following description will be given. The basic principle 2 will be described in detail based on two experimental data.

Experiment 1 FIG. 2 is a block diagram of Experiment 1. From FIG. 2, in Experiment 1,
A three-port optical circulator 132 for separating the injection light 143 and the output light 144, and a three-port optical circulator 132
, A coupling lens 131 for coupling the hybrid mode-locked DBR semiconductor laser 1, and a spectrum analyzer 1
34 are arranged. The spectrum analyzer 134
This is a measuring instrument for measuring the frequency spectrum of the output light.
The other parts are completely the same as the contents described in the configuration of the first embodiment, and thus the description is omitted.

The light pulse repetition frequency 33 used in the experiment
The specifications of the GHz hybrid mode-locked DBR semiconductor laser are as follows. The active layers of the saturable absorption region 101 and the gain region 102 have a gain peak wavelength of 1570 nm.
Nearby InGaAsP / InGaAsP strained multiple quantum well. The length of the saturable absorption region 101 is 75 μm, and the length of the gain region 102 is 750 μm. The waveguides of the passive waveguide region 103 and the DBR region 104 were made of a bulk layer of InGaAsP having a band gap wavelength of 1.3 μm. The length of the DBR region 104 is about 300 μm. The total length of the element was about 1.3 mm.

Experimental Results The following results were obtained by observing a spectrum analyzer without injection light 143 being injected. FIG. 3 is an explanatory diagram of the measurement results of Experiment 1. FIG. 3A shows an optical spectrum measurement result of the self-oscillation light of the hybrid mode-locked DBR semiconductor laser 1. The center wavelength λs is 1559.4.
The spectral width in nm was about 0.54 nm. This value matches the Bragg wavelength of the DBR. The pulse width of the optical pulse is about 6 ps and the pulse repetition frequency is about 3
It was 3 GHz. The laser output has an average intensity of about 10m
W.

Next, the following results were obtained by observing a spectrum analyzer with continuous light having a center wavelength λb = 1563.2 nm and a light intensity of 4 mW injected as the injected light 143 (FIG. 2). FIG. 3B shows that the center wavelength λb = 1 as injection light into the hybrid mode-locked DBR semiconductor laser 1.
It is a measurement result at the time of injecting continuous light of 563.2 nm and light intensity of 4 mW. It can be seen that a new spectral component (wavelength-converted light λt) is generated at a position completely symmetrical with the injected light λb with respect to the spectrum of the self-oscillating light λs. The optical signal of the wavelength converted light λt is the four-wave mixing light. Hereinafter, this four-wave mixing light is referred to as wavelength-converted light λt.

Experiment 2 FIG. 4 is a block diagram of Experiment 2. From FIG. 4, in Experiment 2,
A three-port optical circulator 132 for separating the injection light 143 and the output light 144, the hybrid mode-locked DBR semiconductor laser 1, a three-port optical circulator 132,
A coupling lens 131, a coupling lens 351, a wavelength filter 133, and a wavelength filter 352 are arranged. The coupling lens 351 is a lens that couples the hybrid mode-locked DBR semiconductor laser 1 and the wavelength filter 352. The wavelength filter 352 is a hybrid mode locked DB
This is an optical filter that allows self-oscillation light λs of the R semiconductor laser 1 to pass. The other parts are completely the same as the contents described in the configuration of the first embodiment, and thus the description is omitted.

Experimental Results The output of the wavelength filter 133 and the wavelength filter 3 when a continuous wave of the wavelength λb was injected as the injection light 143 (FIG. 4).
The following results were obtained by observing the output of No. 52 with an SHG correlator. FIG. 5 is an explanatory diagram of the measurement results of Experiment 2. FIG.
(A) is an output waveform of the wavelength filter 352. FIG.
(A) shows that an optical pulse train having a pulse repetition frequency of about 33 GHz is generated. This pulse train is a pulse train based on the self-oscillation light λs of the hybrid mode-locked DBR semiconductor laser 1 (FIG. 4).

FIG. 5B shows an output waveform of the wavelength filter 133. From FIG. 5B, the pulse repetition frequency is about 3
It can be seen that an optical pulse train of 3 GHz is generated. This pulse train is a pulse train based on the wavelength-converted light λt generated inside the hybrid mode-locked DBR semiconductor laser 1 (FIG. 4). When the injection of the injection light 143 is stopped, the output of the wavelength filter 133 is stopped.
It was also confirmed that the output of 52 did not stop.

<Operation of Embodiment 1> FIG. 6 is an explanatory diagram of the operation of Embodiment 1. (A) shows the signal of channel 1 and (b)
Is the signal of channel 2, (c) is the signal of channel 3,
(D) shows a signal of channel 4, (e) shows a 4-channel multiplexed signal, (f) shows a self-oscillation optical pulse train, (g) shows a separated output, and (h) shows (a) to (g). Common time T until
, Respectively. The following preconditions are set for the description of the operation of the specific example 1. Precondition 1 The optical multiplexing / demultiplexing apparatus of the first example (FIG. 1) receives a four-channel multiplexed signal of channel 1, channel 2, channel 3, and channel 4 having the same pulse repetition frequency of fml and separates channel 1. It shall be. Precondition 2 Channel 1, channel 2, channel 3, and channel 4 are all optical signals of the same wavelength λb, and the pulse repetition timing is shifted by １ ／ period for each channel.

Precondition 3 The pulse repetition cycle of the self-oscillating light pulse train of the hybrid mode-locked DBR semiconductor laser 1 is fml.
The frequency of the AC voltage source 125 is also set to fml. Precondition 4 It is assumed that the oscillation timing of the self-oscillation light pulse train (f) matches the timing of the pulse train of channel 1 (a).

The operation of the first embodiment will be described with reference to FIGS. The three-port optical circulator 132 receives the four-channel multiplexed signal (e) at the first port 1321. The four-channel multiplexed signal (e) is output from the second port 1322 of the three-port optical circulator 132 and input to the hybrid mode-locked DBR semiconductor laser 1 via the coupling lens 131.

The four-channel multiplexed signal (e) and the self-oscillation light pulse train (f) are mixed inside the hybrid mode-locked DBR semiconductor laser 1. Hereinafter, description will be given according to time T (h). Time T1 Since the channel 1 (a) and the self-oscillation light pulse train (f) generate pulses, respectively, the optical signal of the wavelength λb and the self-oscillation light pulse train of the channel 1 (a) are explained as described in the basic principle 2. The wavelength conversion light λt is generated by the interaction of the optical signal of the wavelength λs in (f).

As a result, the hybrid mode-locked DBR semiconductor laser 1 combines the composite light composed of the optical signal of the wavelength λb of the channel 1 (a), the optical signal of the wavelength λs of the self-oscillation optical pulse train (f), and the wavelength-converted light λt. The second port 13 of the three-port optical circulator 132 via the lens 131
23. The three-port optical circulator 132 outputs the received mixed light from the third port and sends it to the wavelength filter 133. The wavelength filter 133 passes only the optical signal of the wavelength λt, that is, the wavelength-converted light λt of the channel 1 (a) from the mixed light and outputs the signal. This wavelength-converted light λt becomes a separated output (g).

Time T2 Only the channel 2 (b) generates a pulse, and the self-oscillation light pulse train (f) does not generate a pulse. Therefore, the wavelength converted light λt is not generated. As a result, channel 2
Only the optical signal (b) is input from the hybrid mode-locked DBR semiconductor laser 1 to the second port 1323 of the three-port optical circulator 132 via the coupling lens 131. The three-port optical circulator 132 outputs the received optical signal from the third port to output the wavelength filter 13.
Send to 3. Since the wavelength filter 133 blocks the passage of the optical signal, the separated output (g) is not detected.

Time T3 Only the channel 3 (c) generates a pulse, and the self-oscillation light pulse train (f) does not generate a pulse. Therefore, the wavelength converted light λt is not generated. As a result, channel 3
Only the optical signal (c) is input from the hybrid mode-locked DBR semiconductor laser 1 to the second port 1323 of the three-port optical circulator 132 via the coupling lens 131. The three-port optical circulator 132 outputs the received optical signal from the third port to output the wavelength filter 13.
Send to 3. Since the wavelength filter 133 blocks the passage of the optical signal, the separated output (g) is not detected.

Time T4 All the channels and the self-oscillation pulse (f) do not generate any pulse. Therefore, the separation output (g) is not detected.

Time T5 Since the channel 1 (a) and the self-oscillation pulse (f) generate pulses, respectively, the optical signal of the wavelength λb of the channel 1 (a) and the self-oscillation The wavelength-converted light λt is generated by the interaction of the optical signals having the wavelength λs of the optical pulse train (f).

As a result, the composite light composed of the optical signal of the wavelength λb of the channel 1 (a), the optical signal of the wavelength λs of the self-oscillation optical pulse train (f) and the wavelength-converted light λt is coupled from the hybrid mode-locked DBR semiconductor laser 1. The second port 13 of the three-port optical circulator 132 via the lens 131
23. The three-port optical circulator 132 outputs the received composite light from the third port and sends it to the wavelength filter 133. The wavelength filter 133 passes and outputs only the optical signal of the wavelength λt, that is, the wavelength-converted light of the channel 1 (a) from the composite light. This converted light becomes a separated output (g).

Time T6 Only the channel 2 (b) generates a pulse, and the self-oscillation light pulse train (f) does not generate a pulse. Therefore, the wavelength converted light λt is not generated. As a result, channel 2
Only the optical signal (b) is input from the hybrid mode-locked DBR semiconductor laser 1 to the second port 1323 of the three-port optical circulator 132 via the coupling lens 131. The three-port optical circulator 132 outputs the received optical signal from the third port to output the wavelength filter 13.
Send to 3. Since the wavelength filter 133 blocks the passage of the optical signal, the separated output (g) is not detected.

Time T7 No pulse is generated from all the channels and the self-oscillation pulse (f). Therefore, the separation output (g) is not detected.

Time T8 Only the channel 4 (d) generates a pulse, and the self-oscillation light pulse train (f) does not generate a pulse. Therefore, the wavelength converted light λt is not generated. As a result, channel 4
Only the optical signal (d) is input from the hybrid mode-locked DBR semiconductor laser 1 to the second port 1323 of the three-port optical circulator 132 via the coupling lens 131. The three-port optical circulator 132 outputs the received optical signal from the third port to output the wavelength filter 13.
Send to 3. Since the wavelength filter 133 blocks the passage of the optical signal, the separated output (g) is not detected.

Time T9 Only the self-oscillation pulse (f) generates a pulse, and all channels do not generate a pulse. Therefore, the wavelength converted light λt is not generated. As a result, the self-oscillation pulse (f)
Is input from the hybrid mode-locked DBR semiconductor laser 1 to the second port 1323 of the three-port optical circulator 132 via the coupling lens 131.
The three-port optical circulator 132 outputs the received optical signal from the third port and sends it to the wavelength filter 133. Since the wavelength filter 133 blocks the passage of the optical signal, the separated output (g) is not detected.

To summarize the above results, the optical multiplexing / demultiplexing apparatus of the first embodiment receives the 4-channel multiplexed signal (e) and separates the channel 1 (a). In the above description, according to the precondition 4, the oscillation timing of the self-oscillation light pulse train (f) coincides with the timing of the pulse train of the channel 1 (a).

This is an example, and if the oscillation timing of the self-oscillating light pulse train (f) matches the timing of the pulse train of channel 2 (b), it means that channel 2 (b) has been separated. That is, the channels to be separated can be arbitrarily selected by changing the oscillation timing of the self-oscillation light pulse train (f). In addition, for convenience of explanation, the description is limited to four-channel multiplexing, but the present invention is not limited to this example. That is, the multiplex number can be arbitrarily changed.

<Effect of Specific Example 1> As described above,
In the present invention, since it is not necessary to supply an optical clock signal from the outside, the number of components constituting the device can be reduced, and power consumption can be reduced and the device can be downsized. In addition, there is no need to adjust the polarization state of the optical signal to be demultiplexed, so that there is an effect that optical adjustment becomes easy.

<Structure of Concrete Example 2> FIG. 7 is a structural diagram of Concrete Example 2. According to FIG. 7, the optical multiplexing / demultiplexing device of the first embodiment is
A hybrid mode-locked DBR semiconductor laser 1, a coupling lens 131, a three-port optical circulator 132,
Wavelength filter 133, coupling lens 251, wavelength filter 252, optical detector 253, optical delay circuit 25
4 and a controller 255.

Only the differences from the first embodiment will be described.
The coupling lens 251 is a coupling lens that couples the hybrid mode-locked DBR semiconductor laser 1 and the wavelength filter 252. The wavelength filter 252 is a filter that receives the output light from the hybrid mode-locked DBR semiconductor laser 1 and passes only the converted wavelength light λt from the output light.

The light detector 253 includes the wavelength filter 25.
2 is an optical element for detecting the output light intensity. The optical delay circuit 254 is a part that delays the input optical signal 241.
For example, an optical element that changes the delay time by changing the refractive index by applying an electric field to the optical crystal is used. The controller 255 controls the delay time of the optical delay circuit 254 based on the detection result of the optical detector 253 to maintain the light intensity of the output light of the optical detector 253 at a predetermined level or more (preferably the maximum value). Part. The other parts are the same as in the first embodiment, and the description is omitted.

<Operation of Embodiment 2> The optical multiplexing / demultiplexing apparatus of Embodiment 2 accepts a 4-channel multiplexed signal (FIG. 6 (e)) and separates channel 1 (FIG. 6 (a)). The operation is exactly the same as that of the first embodiment. In the specific example 2, the hybrid mode-locked DBR semiconductor laser 1 is added to the operation of the specific example 1.
The operation of matching the time position (timing) of the self-oscillation pulse (FIG. 6F) with the four-channel multiplexed signal (FIG. 6E) is added.

The operation of the embodiment 2 will be described with reference to FIG. The wavelength filter 252 receives the output light of the hybrid mode-locked DBR semiconductor laser 1 via the coupling lens 251, and passes the wavelength converted light λt from the output light. The level of the wavelength-converted light λt is determined by the self-oscillation pulse (FIG. 6F) and the 4-channel multiplex signal (FIG. 6E).
Indicates the maximum value when the time positions (timings) coincide with each other.

The optical detector 235 receives the wavelength-converted light λt, converts it into an electric signal, and sends it to the controller 255. The controller 255 controls the optical delay circuit 254 based on the detection result of the optical detector 235 to maintain the output of the optical detector 235 at the maximum value. As a result, the time position (timing) of the self-oscillation pulse (FIG. 6 (f)) and the four-channel multiplexed signal (FIG. 6 (e)) are always kept in the same state.

<Effect of Specific Example 2> As described above,
According to the specific example 2, since the time position (timing) of the self-oscillation pulse (FIG. 6 (f)) and the four-channel multiplexed signal (FIG. 6 (e)) can always be maintained in the same state,
In addition to the effects of the first embodiment, it is possible to maintain the long-term stable operation of the wavelength division multiplexing / demultiplexing device.

<Example 3> In Example 2, a self-oscillation pulse (FIG. 6 (f)) and a 4-channel multiplexed signal (FIG. 6 (e))
Although the optical delay circuit 254 is used to maintain the time positions (timings) of the two in the same state, the electric delay line is used in the third embodiment. Hereinafter, the configuration of the specific example 3 will be described.

FIG. 8 is a block diagram of the third embodiment. As shown in FIG. 8, the optical multiplexing / demultiplexing device of the third embodiment includes a hybrid mode-locked DBR semiconductor laser 1, a coupling lens 131,
Port optical circulator 132 and wavelength filter 133
, A coupling lens 251, a wavelength filter 252, an optical detector 253, an electric delay circuit 354, and a control circuit 3.
55.

Only the differences from the second embodiment will be described.
The electric delay circuit 354 is a part that changes the phase of the AC voltage source 125 based on the control of the control circuit 355. The control circuit 355 controls the delay time of the electric delay circuit 354 based on the detection result of the optical detector 253 to maintain the light intensity of the output light of the optical detector 253 at a predetermined level or more (preferably the maximum value). This is the part to do. The other parts are exactly the same as those of the second embodiment, and the description is omitted.

Next, the operation of the third embodiment will be described. In the specific example 2, in order to match the time position (timing) between the self-oscillation pulse (FIG. 6F) and the four-channel multiplexed signal (FIG. 6E), the four-channel multiplexed signal (FIG. 6E) is matched. The delay time was controlled by the optical delay circuit 254 (FIG. 7). On the other hand, in Example 3, the self-oscillation pulse (FIG.
(F)) is delayed to match the time position (timing).

The basic principle of the present invention described in the operation section of the specific example 1 is that the frequency f is applied to the saturable absorption region 101 (FIG. 8).
generating a stable optical pulse train synchronized with the AC voltage source 125 (FIG. 8) from the hybrid mode-locked DBR semiconductor laser 1 (FIG. 8) by applying the AC voltage source 125 (FIG. 8) having a frequency frf near the ml. Can be controlled based on the

The operation of the third embodiment will be described with reference to FIG. The wavelength filter 252 receives the output light of the hybrid mode-locked DBR semiconductor laser 1 via the coupling lens 251, and passes the wavelength converted light λt from the output light. The level of the wavelength-converted light λt indicates a maximum value when the time position (timing) of the self-oscillation pulse (FIG. 6F) matches.

The light detector 253 outputs the wavelength-converted light λ
t is received, converted into an electric signal, and sent to the control circuit 355. The control circuit 355 controls the delay time of the electric delay circuit 354 so that the level of the electric signal indicates the maximum value, and maintains the output of the optical detector 253 at the maximum value. As a result, the time position (timing) of the self-oscillation pulse (FIG. 6 (f)) and the four-channel multiplexed signal (FIG. 6 (e)) can always be maintained in the same state.

<Effect of Specific Example 3> As described above,
According to the third embodiment, unlike the second embodiment, the self-oscillation pulse (FIG. 6 (f)) and the 4-channel multiplexed signal (FIG. 6 (e)) can be obtained even when an inexpensive and easy-to-handle electric delay line is used without using an optical delay line. )
Can always be kept in a state where they coincide with each other.

<Structure of Embodiment 4> FIG. 9 shows the structure of Embodiment 4. As shown in FIG. 9, the optical multiplexing / demultiplexing apparatus of the fourth embodiment includes a hybrid mode-locked DBR semiconductor laser 4, a coupling lens 431b, and an optical signal input optical isolator 432b.
, A coupling lens 431 a, a four-wave mixing light extraction optical isolator 432 a, and a wavelength filter 433.

The hybrid mode-locked DBR semiconductor laser 4 is a synchronous mode laser that oscillates and outputs an optical pulse train having a pulse repetition frequency fm. The details will be described later. The optical signal input optical isolator 432b is
This is a one-way element that transmits the optical multiplexed signal pulse train 441 to the hybrid mode-locked DBR semiconductor laser 4 via the coupling lens 431b, and blocks the output light output from the hybrid mode-locked DBR semiconductor laser 4 from passing therethrough.

The coupling lens 431b is an optical lens for coupling an optical path between the optical signal input optical isolator 432b and the hybrid mode-locked DBR semiconductor laser 4.
The coupling lens 431a is a hybrid mode-locked DBR
An optical lens that couples an optical path between the semiconductor laser 4 and the optical isolator 432a for extracting four-wave mixing light.

An optical isolator 43 for extracting four-wave mixing light
2a is a hybrid mode-locked DBR semiconductor laser 4
Is a one-way element that passes the output light output from the wavelength filter 433 toward the wavelength filter 433 and prevents the return light from the wavelength filter 433 from passing therethrough. The wavelength filter 433 is a filter that receives a composite light composed of the self-oscillation optical pulse train output from the hybrid mode-locked DBR semiconductor laser 4 and the optical multiplexed signal pulse train and outputs only the wavelength converted light λt.

Further, the hybrid mode-locked DBR semiconductor laser 4 has a saturable absorption region 401 and a gain region 40.
2a, a gain region 402b, and a passive waveguide region 403a
, A passive waveguide region 403b, and a DBR region 404a.
, DBR region 404b, n-type common electrode 411, saturable absorber p-side electrode 412, and gain region p-side electrode 413
a, the gain region p-side electrode 413b, the passive waveguide p-side electrode 414a, the passive waveguide p-side electrode 414b, and the DBR
p-side electrode 115a, DBRp-side electrode 115b, saturable absorber reverse bias voltage source 421, gain region current source 4
22a, a gain region current source 422b, a passive waveguide current or reverse bias voltage source 423a, a passive waveguide current or reverse bias voltage source 423b, a DBR current or reverse bias voltage source 424a, a DBR current or reverse bias voltage. A source 424b and an AC voltage source 425 are provided.

The saturable absorption region 401 is a portion that causes mode locking. In this region, an AC voltage source 425 is applied via a saturable absorber p-side electrode 412 and an n-type common electrode 411, and the self-oscillation light pulse train is synchronized with the AC voltage source 425. Gain region 402a
And the gain region 402b are portions that generate light. In this region, the gain region p-side electrode 413a and the n-type common electrode 4
11, the gain region p-side electrode 413b and the n-type common electrode 4
The gain region current source 422a and the gain region current source 422b are applied via 11 to excite carriers to cause oscillation.

The passive waveguide region 403a and the passive waveguide region 403b are waveguides transparent to the oscillation wavelength. In this region, a passive waveguide current or a reverse bias voltage source 423a and a reverse bias voltage source are connected via a passive waveguide p-side electrode 414a and an n-type common electrode 411a, and a passive waveguide p-side electrode 414b and an n-type common electrode 411b. 423b is applied. In the DBR area 404a and the DBR area 404b,
The DBR current or reverse bias voltage source 424a and the DBR current are supplied via the DBRp side electrode 415a and the n-type common electrode 411a, and the DBRp side electrode 415b and the n-type common electrode 411b.
An R current or a reverse bias voltage source 424b is applied. It is also a region provided with a DBR that determines an oscillation wavelength and an oscillation wavelength width, that is, a diffraction grating.

The above description is summarized as follows. The left side of the L1-L2 cross section in FIG. 9 has the same configuration as the hybrid mode-locked DBR semiconductor laser 1 of the first embodiment (FIG. 1), and the left side configuration of the L1-L2 cross section corresponds to L1.
The configuration on the right side of the -L2 section is line-symmetric with respect to the L1-L2 section. That is, in the hybrid mode-locked DBR semiconductor laser 4 of Example 4, the saturable absorption region 401 is disposed in the center of the internal optical path, and the DBR regions 404a and 404b are disposed on the side surfaces of both ends of the optical path. Have been.

<Operation of Specific Example 4> First, the operation of the hybrid mode-locked DBR semiconductor laser 4 in a state where the optical multiplexed signal pulse train 441 is not input will be described with reference to FIG. A saturable absorber reverse bias voltage source 421;
Gain region current source 422a and gain region current source 422b
And a passive waveguide current or reverse bias voltage source 423a.
And a passive waveguide current or reverse bias voltage source 423b.
A DBR current or reverse bias voltage source 424a;
By applying a predetermined current and a reverse bias voltage to the DBR current or the reverse bias voltage source 424b, the hybrid mode-locked DBR semiconductor laser 4 generates a self-oscillating optical pulse train having a pulse repetition frequency fml that matches the laser circulating frequency or an integral multiple thereof. Generate. Next, when a sine of a frequency frf approximating fml is applied to the saturable absorption region 401, the hybrid mode-locked DBR semiconductor laser 4 generates a stable self-oscillating light pulse train with small time jitter according to the basic principle 1. The wavelength of the self-oscillation light pulse train generated at this time is the DBR region 404.
Of the Bragg wavelength λs.

Next, as in the first embodiment, an optical multiplexed signal pulse train 441 (corresponding to (e) in FIG. 6) is transmitted to the hybrid mode-locked DBR semiconductor laser 4 via the optical signal input optical isolator 432b and the coupling lens 431b. Is input to At this time, as in the first embodiment, the hybrid mode synchronization D
The self-oscillation light pulse train inside the BR semiconductor laser 4 (FIG. 6)
(Corresponding to (f)) is used as excitation light to generate wavelength-converted light λt (the four-wave mixed light) of the optical multiplexed signal pulse train 441. This wavelength-converted light λt is coupled to the coupling lenses 431a,
The light passes through the wave mixing light extraction optical isolator 432a and the wavelength filter 433, and is output as a demultiplexed signal 442 (corresponding to (g) in FIG. 6).

The difference from the first embodiment will be described. In the specific example 1, the path (optical path length) in which the optical multiplexed pulse train 141 (FIG. 1) and the self-oscillation light pulse train generate the wavelength-converted light λt by interaction starts from the left end of the DBR region 104 (FIG. 1), The light is reflected at the right end of the saturable absorption region 101 (FIG. 1) and reaches the left end of the DBR region 104 (FIG. 1) again.

On the other hand, in the specific example 4, the optical multiplex signal pulse train 4
41 (FIG. 9) and a path (light path length) in which the self-oscillation light pulse train generates the wavelength-converted light λt by the interaction is DBR
Starting from the left end of region 404a (FIG. 9), DBR region 4
04b (FIG. 9). The distance between the paths that generate the wavelength-converted light λt is equal. But specific example 1
It should be noted that there is a reflective surface in the middle.
Normally, the reflectance at this reflecting surface is around 20%. On the other hand, in the specific example 4, there is no reflection surface in the middle, so that the loss due to the reflection surface is zero. As a result, in the specific example 4, the light intensity of the optical multiplexed signal pulse train 441 (FIG. 9) and the self-oscillation optical pulse train involved in the interaction are greatly enhanced as compared with the specific example 1.

<Effect of Specific Example 4> As described above,
According to the fourth embodiment, since the light intensity of the optical multiplex pulse train and the self-oscillation light pulse train involved in the interaction is greatly enhanced as compared with the first embodiment, the light intensity of the wavelength-converted light λt is also enhanced. As a result, in addition to the effect of the first embodiment, the S / N of the output light demultiplexed is greatly improved, and a stable operation is maintained.

<Structure of Embodiment 5> FIG. 10 is a diagram showing the structure of Embodiment 5. As shown in FIG. 10, the optical multiplexing / demultiplexing device according to the fifth embodiment includes a hybrid mode-locked DBR semiconductor laser 4,
Coupling lens 431b and optical isolator 4 for optical signal input
32b, a coupling lens 431a, an optical isolator 432a for extracting four-wave mixing light, a wavelength filter 433,
It comprises an optical splitter 551, an optical detector 552, an optical delay circuit 553, and a controller 554.

Only the differences from the fourth embodiment will be described.
The optical splitter 551 is an optical coupler that separates and extracts a part of the output light. The optical detector 552 includes an optical demultiplexer 551.
Is an optical element for detecting the output light intensity of the optical element. Optical delay circuit 5
Numeral 53 denotes a part for delaying the optical multiplex signal pulse train 541. For example, an optical element that changes the delay time by changing the refractive index by applying an electric field to the optical crystal is used. The controller 554 controls the delay time of the optical delay circuit 553 based on the detection result of the optical detector 552. The other parts are the same as in the specific example 4, and the description is omitted.

The optical multiplexing / demultiplexing apparatus according to the fifth embodiment differs from the operation according to the fourth embodiment in that the hybrid mode-locked DBR semiconductor laser 4
The operation of matching the time position (timing) of the self-oscillation optical pulse train and the optical multiplexed signal pulse train 541 is added.
The operation of the specific example 5 will be described with reference to FIG. The wavelength filter 433 receives the output light of the hybrid mode-locked DBR semiconductor laser 4 via the coupling lens 431a and the optical isolator for extracting four-wave mixing light, and passes the converted wavelength light λt from the output light. The level of the wavelength-converted light λt depends on the self-oscillation light pulse train and the
The maximum value is shown when the time positions (timings) of 41 match.

The optical detector 552 receives the wavelength-converted light partially separated from the wavelength filter 433 by the optical demultiplexer 551, converts the light into an electric signal, and sends the electric signal to the controller 554.
The controller 554 controls the delay time of the optical delay circuit 553 so that the level of the electric signal indicates the maximum value, and maintains the output of the optical detector 552 at the maximum value. As a result, the time position (timing) of the self-oscillation optical pulse train and the optical multiplexed signal pulse train 541 can always be maintained in the same state.

<Effect of Specific Example 5> As described above,
According to the fifth embodiment, the time position (timing) of the self-oscillation light pulse train and the optical multiplex pulse train can always be maintained in the same state. Therefore, in addition to the effect of the fourth embodiment, the long-term stable operation of the wavelength division multiplexer is maintained. It becomes possible to do.

<Embodiment 6> FIG. 11 is a block diagram of Embodiment 6. As shown in FIG. 11, the optical multiplexing / demultiplexing device of the specific example 6 includes a hybrid mode-locked DBR semiconductor laser 4, a coupling lens 431b, and an optical signal input optical isolator 432b.
, A coupling lens 431a, an optical isolator 432a for extracting four-wave mixing light, a wavelength filter 433, an optical demultiplexer 551, an optical detector 552, and an electric delay circuit 65.
1 and a control circuit 652.

Only the differences from the fifth embodiment will be described.
The control circuit 652 is a part that receives the output of the optical detector 552 and controls the delay time of an electric delay circuit 651 described later. The electric delay circuit 651 includes a control circuit 652
Is a part that changes the phase of the AC voltage source 425 based on the control of. The other parts are exactly the same as in the specific example 5, and the description is omitted.

Next, the operation of the embodiment 6 will be described. In the specific example 5, the delay time of the optical multiplexed signal pulse train 541 (FIG. 10) is set to the optical delay circuit 553 (FIG. 10) in order to match the time position (timing) of the self-oscillation optical pulse train and the optical multiplexed signal pulse train 541 (FIG. 10). ). On the other hand, in Example 6, the time position (timing) is matched by delaying the self-oscillation light pulse train.

The basic principle of the present invention described in the operation section of the specific example 1 above is that the AC voltage source 125 (FIG. 8) having a frequency frf near the frequency fml is applied to the saturable absorption region 101 (FIG. 8).
To apply the hybrid mode-locked DBR
AC voltage source 125 (FIG. 8) from semiconductor laser 1 (FIG. 8)
It can generate a stable optical pulse train synchronized with
Control based on

The operation of the embodiment 6 will be described with reference to FIG. The wavelength filter 433 receives the output light of the hybrid mode-locked DBR semiconductor laser 4 via the coupling lens 431a and the four-wave mixing light extraction optical isolator 432a, and passes the converted wavelength light λt from the output light.
The level of the wavelength-converted light λt has a maximum value when the time position (timing) of the self-oscillation light pulse train and the optical multiplex pulse train (FIG. 11) match.

The optical detector 552 receives a part of the wavelength-converted light λt from the optical splitter 551, converts it into an electric signal, and sends it to the control circuit 652. The control circuit 652 controls the electric delay circuit 651 so that the level of the electric signal indicates the maximum value.
To maintain the output of the optical detector 552 at the maximum value. As a result, the time position (timing) of the self-oscillating optical pulse train and the optical multiplexed pulse train can always be maintained in a state of being coincident.

<Effect of Specific Example 6> As described above,
According to the specific example 6, unlike the specific example 5, even when an inexpensive and easy-to-handle electric delay line is used without using an optical delay line, the time positions (timings) of the self-oscillating optical pulse train and the optical multiplexed pulse train always coincide. Can be maintained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a specific example 1.

FIG. 2 is a configuration diagram of Experiment 1.

FIG. 3 is an explanatory diagram of measurement results of Experiment 1.

FIG. 4 is a configuration diagram of Experiment 2.

FIG. 5 is an explanatory diagram of measurement results of Experiment 2.

FIG. 6 is an operation explanatory diagram of the first specific example.

FIG. 7 is a configuration diagram of a specific example 2.

FIG. 8 is a configuration diagram of a specific example 3.

FIG. 9 is a configuration diagram of a specific example 4.

FIG. 10 is a configuration diagram of a specific example 5;

FIG. 11 is a configuration diagram of a specific example 6.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 hybrid mode-locked DBR semiconductor laser 101 saturable absorption region 102 gain region 103 passive waveguide region 104 DBR region 111 n-type common electrode 112 saturable absorber p-side electrode 113 gain region p-side electrode 114 passive waveguide p-side electrode 115 DBRp side electrode 121 Saturable absorber reverse bias voltage source 122 Gain area current source 123 Passive waveguide current or reverse bias voltage source 124 DBR current or reverse bias voltage source 125 AC voltage source 131 Coupling lens 132 3-port optical circulator 133 Wavelength filter

Claims (8)

[Claims] 1. An optical multiplexed pulse train in which an N-channel optical pulse train is subjected to optical time division multiplexing (OTDM) is received from a first port and transmitted to a mode-locked DBR semiconductor laser via a second port. A self-oscillating optical pulse train generated by a semiconductor laser, the optical multiplexed pulse train, and a composite light including four-wave mixing light generated by an interaction between the self-oscillating optical pulse train and the optical multiplexed pulse train is output from the second port. An optical circulator for receiving and outputting to the third port; and an optical wavelength filter for receiving the optical composite light from the third port of the optical circulator and outputting only the four-wave mixing light, the mode-locked DBR semiconductor laser. Generates a self-oscillating optical pulse train at a frequency of 1 / N of the pulse repetition frequency of the optical multiplex pulse train. An optical multiplexing / demultiplexing apparatus, wherein a timing at which an oscillation light pulse train is generated coincides with any channel of the optical multiplex pulse train, and a wavelength of the self-oscillation light pulse train is different from a wavelength of the optical multiplex pulse train. 2. The optical demultiplexing device according to claim 1, wherein the mode-locked DBR semiconductor laser includes: a saturable absorption region that synchronizes the self-oscillation light pulse train with an externally applied AC voltage source; A DBR region having a diffraction grating corresponding to the wavelength of the self-oscillation light pulse train is arranged, and an AC voltage source of 1 / N of a pulse repetition frequency of the optical multiplex pulse train is applied to the saturable absorption region. An optical demultiplexer, wherein a part of the self-oscillating light pulse train to be synchronized is reflected by the DBR region. 3. The optical multiplexing / demultiplexing device according to claim 1, wherein an optical delay circuit for delaying a timing at which the optical multiplexed pulse train is input to the mode-locked DBR semiconductor laser; and the mode-locked DBR. An optical detector that receives a part of the four-wave mixing light output from the semiconductor laser and detects the light intensity thereof, and a controller that controls a delay time of the optical delay circuit, wherein the controller has a detection result of the optical detector. An optical multiplexing / demultiplexing device for controlling a delay time of the optical delay circuit based on the optical delay circuit to maintain the light intensity of the four-wave mixing light at a predetermined level or more. 4. The optical multiplexing / demultiplexing device according to claim 1, wherein an electric delay circuit for delaying a timing at which the AC voltage source is applied to the saturable absorption region, and the mode-locked DBR semiconductor. An optical detector that receives a part of the four-wave mixing light output by the laser and detects the light intensity thereof, and a control circuit that controls a delay time of the electric delay circuit, wherein the control circuit detects the optical detector. An optical multiplexing / demultiplexing device, wherein a delay time of the electric delay circuit is controlled based on a result to maintain a light intensity of the four-wave mixing light at a predetermined level or more. 5. An optical isolator for inputting an optical signal, which receives an optical multiplexed pulse train obtained by subjecting an N-channel optical pulse train to optical time division multiplexing (OTDM) and sends it to a mode-locked DBR semiconductor laser; Receiving from the mode-locked DBR semiconductor laser an optical composite light consisting of a self-oscillating optical pulse train, the optical multiplexed pulse train, and four-wave mixing light generated by the interaction of the self-oscillating optical pulse train and the optical multiplexed pulse train. An optical isolator for extracting four-wave mixing light to be sent to an optical wavelength filter, and an optical wavelength filter for receiving the optical composite light from the optical isolator for extracting four-wave mixing light and outputting only the four-wave mixing light, the mode The synchronous DBR semiconductor laser has a frequency of 1 / N of a pulse repetition frequency of the optical multiplex pulse train. Self-oscillates, the timing at which this self-oscillation light pulse train is generated coincides with any channel of the optical multiplex pulse train, and the wavelength of the self-oscillation light pulse train is different from the wavelength of the optical multiplex pulse train. Optical demultiplexer. 6. The optical multiplexing / demultiplexing device according to claim 5, wherein the mode-locked DBR semiconductor laser synchronizes the self-oscillation light pulse train with an externally applied AC voltage source at a central portion of an internal optical path. A saturable absorption region to be provided, and a DBR region provided with a diffraction grating corresponding to the wavelength of the self-oscillation light pulse train at both ends of the optical path; An optical multiplexing / demultiplexing apparatus, wherein N alternating current voltage sources are applied, and a part of the self-oscillating light pulse train synchronized with the alternating current voltage source is reflected between the DBR regions. 7. The optical multiplexing / demultiplexing device according to claim 5, wherein an optical delay circuit for delaying a timing at which the optical multiplexed pulse train is input to the mode-locked DBR semiconductor laser; and the mode-locked DBR. An optical detector that receives a part of the four-wave mixing light output from the semiconductor laser and detects the light intensity thereof, and a controller that controls a delay time of the optical delay circuit, wherein the controller has a detection result of the optical detector. An optical multiplexing / demultiplexing device for controlling a delay time of the optical delay circuit based on the optical delay circuit to maintain the light intensity of the four-wave mixing light at a predetermined level or more. 8. The optical multiplexing / demultiplexing apparatus according to claim 5, wherein an electric delay circuit for delaying a timing at which the AC voltage source is applied to the saturable absorption region, and the mode-locked DBR semiconductor. An optical detector that receives a part of the four-wave mixing light output by the laser and detects the light intensity thereof, and a control circuit that controls a delay time of the electric delay circuit, wherein the control circuit detects the optical detector. An optical multiplexing / demultiplexing device, wherein a delay time of the electric delay circuit is controlled based on a result to maintain a light intensity of the four-wave mixing light at a predetermined level or more.