JP2001027769A - Light time division multiplexed separating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute light time division multiplexed separation of a light pulse string with high efficiency while preventing the reduction of intensity of a signal light pulse. SOLUTION: This device is composed of a 4-light wave mixing element 4 which generates phase conjugate light from an incident exciting light pulse and an incident signal light pulse string, a phase conjugate light separating means 5 which selectively takes out the phase conjugate light, and an exciting light pulse delay means 7, 8 which emit exciting light pulses with a time difference of the integral multiple of the signal light pulse interval in the signal light pulse string by receiving the exciting light pulse and the signal light pulse strings outputted from the 4-light wave mixing element 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical time division multiplexing / demultiplexing apparatus.

[0002]

2. Description of the Related Art An optical time-division multiplexing method as illustrated in FIG. 1 is known as a method for transmitting a large amount of information using an optical transmission line composed of one optical fiber. In the optical time division multiplexing method, an optical circuit that can follow an ultra-high-speed optical signal does not exist on the receiving side, but a time-division multiplexed and separated optical signal is received in an optical state by an optical receiver. Therefore, a device capable of demultiplexing an ultrahigh-speed optical pulse is required.

In FIG. 1, an output section of an ultrashort optical pulse light source 101 using a Q switch has N optical fibers 1.
N optical modulators 103 are connected in parallel via the optical modulator 02. These optical modulators 103 include the ultrashort light pulse light source 1
Light modulation is performed on the ultrashort light pulse output from 01 to output a modulated pulse. Then, N delay lines 104a _{1 to} 104a connected to the respective output units of the N optical modulators 103
_n has a function of sending modulated optical pulses to the optical coupler 105 at different timings. The optical pulse train superimposed by the optical coupler 105 has several hundred Gb / s or more.
The signal is transmitted to the optical transmission line 106 as an optical signal having a frequency of 1 Tb / s.

On the other hand, an optical signal (optical pulse train) transmitted through the optical transmission line 106 is divided into N signals by an optical distributor 112 on the receiving side. Are sent to the optical switches 107. Then, the N optical switches 107 time-divide the optical signal at different timings to separate the optical pulses one by one. The optical pulses separately output from the N optical switches 107 are input to different optical receivers 109 via the optical fiber 108.

The input side of each optical switch 107 has:
Different N number of delay lines 110a of lengths _1-110
control light pulse is input from the control light pulse source 111 through a _n. The optical switch 107 is made of a medium having a supersaturation absorption effect. The supersaturated absorption effect is an effect that becomes transparent when light enters, and is a kind of optical nonlinear effect.

Therefore, when a control light pulse is input from the control light pulse light source 111 to the optical switch 107, the optical switch 1
The medium 07 is made transparent by the control light pulse, and the signal light from the optical transmission line 106 passes through the optical switch 107 only while the control light pulse is incident. As a result, when the control light pulse enters the optical switch 107 of each channel at a different timing, only the required optical pulse train is output to the receiver 109 of each channel.

The optical time-division separation device is disclosed in JP-A-8-152656, JP-A-8-172395, JP-A-10-173634, and JP-A-10-173634.
No. 178418. In the above description,
Although the case where the saturable absorption effect is used as the optical nonlinear effect has been described, a method using the four-wave mixing effect has also been proposed. Using such a four-wave mixing effect, for example,
S. Kawanishi, T. Morioka, O. Kamatani, H. Takara,
JM Jacob and MSaruwatari, "100 Gbit / s all-optic
al demulti; lexingusing four-wave mixing in a trave
lling wave laser diode amplifier "Electron. Lett.
Vol. 30, No. 12, pp. 981-982, 1994.

In four-wave mixing, when control light (angular frequency ω _p ) and signal light (angular frequency ω _s ) enter a nonlinear medium, phase conjugate light (angular frequency 2ω _p −ω _s ) is generated. The effect is. An optical time division demultiplexing device using the four-wave mixing effect is disclosed in, for example, Japanese Patent Application Laid-Open Nos.
It is described in JP-A-172395.

[0009]

According to the above-described configuration, the signal light pulse train and the control light pulse are divided into N channels, and their intensities are reduced. As the generation source 111, a high-output short-pulse generation source is required. The optical switch 10
When a temporal shift occurs in the control light pulse incident on 7,
There is a problem that efficiency is deteriorated because the light enters other channels.

An object of the present invention is to provide an optical time division multiplexing / demultiplexing apparatus capable of performing optical time division multiplexing / demultiplexing of an optical pulse train with high efficiency while preventing the intensity of a signal light pulse from decreasing.

[0011]

Means for Solving the Problems The above-mentioned problem is solved by referring to FIGS.
As exemplified in FIG. 9, a four-wave mixing element 4 for generating a phase conjugate light by injecting an excitation light pulse and a signal light pulse train.
A phase conjugate light separating means 5 for selectively extracting the phase conjugate light; and an excitation light pulse and a signal light pulse train which are output from the four-wave mixing element 4 (21, 28). An optical time-division multiplexing / demultiplexing apparatus characterized by having pump light pulse delay means (7, 8 (18)) for emitting pulses with a time difference of an integral multiple of the signal light pulse interval of the signal light pulse train. Is done.

In the above optical time division multiplexing / demultiplexing apparatus,
The signal light pulse train is a light pulse train multiplexed n times (n is an integer), and n four-wave mixing elements 4 are connected in series. In the above-described optical time-division multiplexing / demultiplexing apparatus, the four-wave mixing element 21 may be constituted by a semiconductor optical amplifier. In this case, the excitation light pulse and the signal light pulse train have different wavelengths, and a DC light incidence means 23 having a higher intensity than the excitation light pulse and the signal light pulse train is attached to the incident end of the semiconductor amplifier 21. A structure may be adopted. Further, a plurality of the four-wave mixing elements 21 are connected in series, and a part of the output light of the four-wave mixing
A structure having an optical feedback unit 25 for returning to the input terminal of the four-wave mixing element 21 of the first stage through the first stage may be adopted.

The figures and reference numerals described above are cited for facilitating the understanding of the present invention, and the present invention is not limited thereto. Next, the operation of the present invention will be described. According to the present invention, the excitation light pulse and the signal light pulse train are incident on the four-wave mixing element to generate phase conjugate light,
The phase conjugate light is selectively extracted, read out as a signal light pulse to be detected, and the excitation light pulse and the signal light pulse train output from the four-wave mixing element are input to the next four-wave mixing element. First, the excitation light pulse is given a time difference by an integral multiple of the light pulse interval of the signal light pulse train.

The phase conjugate light is adjusted so as to be generated by a four-wave mixing effect of one light pulse of the signal light pulse train and an excitation light pulse synchronized with the light pulse. The excitation light pulse and the signal light pulse train that pass through the four-wave mixing element pass through the element as they are even after generating the phase conjugate light. After the phase conjugate light is generated by one four-wave mixing device, the arrival times of the excitation light pulse and the signal light pulse train are shifted by the light pulse interval so as to be incident on the next four-wave mixing device. . Then, in the four-wave mixing element in the next and subsequent stages,
Each phase conjugate light is generated, and this is used as a signal light pulse to be detected.

Therefore, since it is not necessary to divide the signal light pulse train into a plurality, the light intensity does not decrease. In addition, since the pump light pulse has a time difference of an integral multiple of the signal light pulse train, the original nth light pulse in the signal light pulse train and the pump light pulse are reliably synchronized to generate a phase shared light. , Efficiency is improved.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention. (First Embodiment) FIG. 2 is a block diagram showing an optical time division multiplexing / demultiplexing apparatus according to an embodiment of the present invention. FIG.
1 is a configuration diagram of a block of an optical time division multiplexing / demultiplexing device according to a first embodiment of the present invention.

[0017] In FIG. 2, the signal optical pulse train P _s and the control light pulse P _c is n which are connected in series (n> 1) the light separating optical circuit A ₁ of the _stage, A _2, ..., is transmitted to A _n .., And a predetermined optical signal pulse is separated by the optical separation optical circuits A _1, A ₂ ,. Each of the light separating optical circuits A _1, A ₂ ,... Has a configuration as shown in FIG.

[0018] First, in the first stage optical separation optical circuit A ₁ shown in FIG. 3, the signal optical pulse train P _s signal transmitting optical fiber 1 and the control light for transmitting (excitation light) pulse P
Each output end of the control light transmitting optical fiber 2 for transmitting _c is coupled by an optical coupler 3. The output end of the optical coupler 3 is connected to one end of a dispersion shift fiber 4 having a length of, for example, 3.0 km as a four-wave mixing element for generating a phase conjugate light pulse _Pr1. A wavelength router 5 is connected to the end. The wavelength router has a function of making the direction in which light propagates depending on the wavelength, and is composed of, for example, a diffraction grating.

The output section of the wavelength router 5 has first to third
Are connected in parallel, the phase conjugate optical pulse _Pr1 separated by the wavelength router 5 is sent into the first optical fiber 6, and the control optical pulse _Pc is sent into the second optical fiber 7. the feed is configured to send a signal optical pulse train P _s to a third optical fiber 8. First optical fiber 6
Is connected to the optical receiver 9 so that only the phase conjugate light pulse _Pr1 is input to the optical receiver 9.

Further, the second optical fiber 7 for propagating control pulse P _c has, for example, 3mm long optical path difference compared to the third optical fiber 8 for propagating signal light pulse train P _s, which by, and reaches the optical coupler 10 of the control pulse P _c is the signal optical pulse train P _s 1 pulse interval than (e.g. 10 picoseconds (ps)) delayed by a second stage optical separation optical circuit a ₂ Has been adjusted as follows.

The second-stage optical separation circuit A ₂ has the same configuration as the first-stage optical separation circuit A ₁ . That is, the second stage of the output end of the optical coupler 10 of the optical separating optical circuit A _2, the dispersion of the four-wave mixing element that generates a phase conjugate light pulse P _r2 e.g. length 3.0km shifted fiber 11 Are connected at one end. The other end of the dispersion shift fiber 11 is connected to a wavelength router 12.

The output section of the wavelength router 12 has first to
The third optical fibers 13 to 15 are connected in parallel,
The phase conjugate light pulse _Pr2 separated by the wavelength router 12 is sent into the optical receiver 16 via the first optical fiber 13,
The feed control pulses P _c to the second optical fiber 14, and is configured to send a signal optical pulse train P _s to a third optical fiber 15.

The second optical fiber 14 for propagating a control optical pulse P _c, the third for propagating signal light pulse train P _s
Of having, for example, 3mm long optical path difference than the optical fiber 15, thereby, the control pulse P _c is the signal optical pulse train P
It is adjusted so as to reach the 1 pulse interval (e.g., 10 picoseconds (ps)) delayed by a third stage optical coupler light separation optical circuit A ₃ shown in FIG. 2 than _s.

The optical separating optical circuit of the third and subsequent stages A ₃ to A _n
Also has the same configuration as the first and second optical separation optical circuits A ₁ and A _{2. In} these optical separation optical circuits, a predetermined phase conjugate light pulse is transmitted by the light receiving element. It is designed to receive light. Next, the operation of the optical time division multiplexing / demultiplexing device having the above configuration will be described. First, wavelength 1.
Optical signal pulse pulse with a pulse width 1ps in 56μm are arranged in 10ps intervals column P _s the signal transmission optical fiber 2
And a pulse width of 1p at a wavelength of 1.55 μm.
The control pulse of s is input to the control light transmitting optical fiber 1. In this case, control pulse P _c is first incident in synchronization with the control light transmission optical fiber 1 to a first optical pulse to be sent of the optical signal pulse P _s.

[0025] These signal optical pulse train P _s and the control light pulse P _c is input through an optical coupler 3 and the dispersion-shifted fiber 4 in wavelength router 5. In dispersion-shifted fiber 4, occurs four-wave mixing based on the control pulse P _c of a first optical pulse and the angular frequency omega _p of the angular frequency omega _s of the signal optical pulse train P _s 4 corners Frequency (2ω _p
Because the phase conjugate light pulse P _r of - [omega] _s) is generated, three pulses in wavelength router 5, that is, the signal optical pulse train P _s, control pulse P _c and the phase conjugate light pulse P _r is inputted. The wavelength of the phase conjugate light pulse P _r is 1.54
01 μm.

[0026] Then, the intensity of the phase conjugate light pulse P _r of those three kinds of light pulses varies in accordance with the intensity of the first light pulse, the first optical pulse of the optical signal pulse train P _s Is input to the optical receiver 9 through the first optical fiber. Further, the optical signal pulse train P _s which is controlled propagation direction by the wavelength router 5, the third optical fiber 8
Through the optical coupler 10 of the second-stage optical separation optical circuit A ₂
To enter.

The control pulse P _c, which is controlling the direction by the wavelength router 5, with a delay of 10ps than the signal optical pulse train P _s while passing through the second optical fiber 8, for optical separation of the second stage input to the optical coupler 10 of the optical circuit a _2. Thus, the control pulse P _c is input to the signal optical pulse train P _s second-th second stage wavelength router 12 of the light separation optical circuit A ₂ in synchronism with the optical pulses.

The control light pulse P _c and the signal light pulse train P _s combined by the optical coupler 10 are input to the wavelength router 12 through the dispersion shift fiber 11. And
In the dispersion shift fiber 11, the signal light pulse train P
_s phase conjugate light pulses of the second wavelength 1.5401μm by a four light mixing effect of the light pulse and the control optical pulse P _c is has been wavelength router 12 input generation of.

[0029] Then, the signal optical pulse train P _s, control pulse P _c and the phase conjugate light pulse P _r is separated into first to third optical fibers 13 to 15 by the wavelength router 12, respectively. Among them, the intensity of the phase conjugate light pulse P _r, since changes in accordance with the intensity of the second optical pulse of the optical signal pulse train P _s, the optical receiver as the second optical pulse of the optical signal pulse train P _s 9 Will be read by

Furthermore, the optical signal pulse train P _s is input to the third of the third stage optical coupler light separation optical circuit A ₃ shown in FIG. 4 through an optical fiber 15. Further, the control pulse P _c, while passing through the second optical fiber 14, a delay of 10ps than the optical signal pulse train P _s, the third stage in synchronization with the third optical pulse signal optical pulse train P _s entering the eyes of the optical coupler of the optical separating optical circuit a _3.

[0031] Since then, up to the light separation optical circuit A _n of the final stage, the control pulse P _c, the optical signal pulse train P _s n number of sequential delay of one signal light pulse interval to light pulses While inputting to the photodetector, and further controlling light pulse P
_c and the optical signal pulse train P _s will generate four light mixed wave pulses while passing through the dispersion-shifted fiber will be detected as a signal light by separating the four-wave mixing wave light pulse.

That is, the control light pulse P _c is incident on the next four-wave mixing element with a time difference of an integral multiple of the signal light pulse interval, and the four-wave mixing element controls the control light pulse. N of the optical signal pulse train P _s synchronized with P _c
A four-wave mixed wave pulse corresponding to the intensity of the light pulse is generated. By adopting the above configuration, it is not necessary to divide the control light pulse and the signal light pulse train into n pieces, so that the intensity of these light pulses is prevented from being reduced, and the synchronization is eliminated to be extremely efficient. Optical time division multiplexing / demultiplexing can be performed. (Second Embodiment) On the output side of the wavelength router 5 of the optical time division multiplexing / demultiplexing apparatus shown in the first embodiment, in addition to the optical fiber 6 for extracting four-wave mixing optical pulses,
The optical fibers 7 and 8 are connected so that a signal light pulse train propagates through one of the optical fibers 8 and a signal light pulse train propagates through the other optical fiber 8.

In this embodiment, a structure in which a control optical pulse and a signal optical pulse train are propagated by one optical fiber connected to the wavelength router 5 will be described. FIG. 5 is an optical time division multiplexing / demultiplexing apparatus according to a second embodiment of the present invention, and the same reference numerals as those in FIG. 3 indicate the same elements. 5, the output of the first stage wavelength router 5 of the light separation optical circuit A ₁ is
The first optical fiber 6 connected to the photodetector 9 and the second optical fiber 18 connected to the second-stage optical separation optical circuit A ₂ are connected. pulse train P _s and the control light pulse P _c is adapted to propagate.

The second optical fiber 18 is 18 ps /
It consists of a normal single mode optical fiber with a dispersion of nm / km. The optical wavelength of the optical signal pulse train P _s and 1.56 .mu.m, the control light pulse wavelength of P _c as the wavelength of 1.55 .mu.m, the control pulse P _c is the signal light and propagates in the single mode optical fiber with a length of 550m delay of 10ps is generated compared to the pulse train P _s.

Therefore, the length of the second optical fiber 18 is set to 5
If the distance is 50 m, the control light pulse P _c and the signal light pulse train P
_s is, when the input to the second stage of the dispersion-shifted fiber 18 of the optical separating optical circuit A _2, the control signal pulse P _c is synchronized with the second optical pulse of the optical signal pulse train P _s. Then, in the dispersion-shifted fiber 17 of the _second optical separation optical circuit A2, a four-wave mixing pulse _Pr2 is generated by the four-wave mixing effect as in the first embodiment.

[0036] In a second wavelength router 12 of the light separation optical circuit A _2, as the second optical pulse signal of the optical signal pulse train P _s through the first optical fiber 16 four-wave mixed light pulse is separated Taken out. Further, the dispersion-shifted fiber (not shown of the control light pulses separated by wavelength router 12 P _c and the signal optical pulse train P _s is the next-stage light separation optical circuit A _n through the second optical fiber 19 of length 550m ).

In order to avoid deterioration of the waveforms of the control light pulse and the signal light pulse train, the width of one light pulse is set to 10 p.
It is preferred to be about s. According to the present embodiment, similarly to the first embodiment, since it is not necessary to divide the control light pulse and the signal light pulse train into n pieces, a decrease in the intensity of those light pulses is prevented, and furthermore, the synchronization shift is prevented. Thus, optical time division multiplexing and demultiplexing can be performed very efficiently, and the number of optical fibers connected to the output side of the wavelength router is reduced as compared with the first embodiment. (Third Embodiment) In the optical time-division multiplexing / demultiplexing apparatus described in the first embodiment, a dispersion-shifted fiber is used to generate four-wave mixing light pulses. However, a wave-optical amplifier is used instead of the dispersion-shifted fiber. The configuration may be used, and the configuration will be described with reference to FIG. In FIG. 6, the same reference numerals as those in FIG. 3 indicate the same elements.

The first-stage light separating optical circuit A shown in FIG.
In _1, between the optical coupler 3 and the wavelength router 5, the semiconductor optical amplifier 21 for propagating a control optical pulse P _c and the signal optical pulse train P _s are connected via the optical fiber 20. The semiconductor optical amplifier 21 can obtain sufficiently detectable phase conjugate light even with a device length of about 1 mm in order to cause a strong four-wave mixing effect. Therefore, an optical time division multiplexing / demultiplexing device using such a semiconductor optical amplifier 21 is downsized.

As the semiconductor optical amplifier 21, for example,
There is a 1.55 μm band semiconductor Fabry-Perot laser in which both end faces are non-reflectively coated. Signal optical pulse train P _s and the control light pulse P to the entrance end of such a semiconductor optical amplifier 21
When incident _c, the optical signal pulse train P _s and the control light pulse P _c and the four-wave mixed light pulse P _r1 is output to the wavelength router 5 from the output end of the semiconductor optical amplifier 21, wavelength router 5, the four-wave that The mixed light pulse _Pr1 is separated and output to the photodetector 9 through the optical fiber 6.
Its four-wave mixed light pulse P _r1 is the first stage of the light separation optical circuit A ₁ is detected as the first optical pulse of the optical signal pulse train P _s, light for optical separation of the n-th stage circuit A _n Is detected as the n-th light pulse of the signal light pulse train. (Fourth Embodiment) As described in the third embodiment, if a strong control light pulse is applied to a semiconductor optical amplifier, the gain of the semiconductor optical amplifier may fluctuate and the waveform may be distorted.

In such a case, as shown in FIG.
The first stage of the semiconductor optical amplifier 21 of the light separating optical circuit A ₁
Is connected to the input end of the optical fiber 23 via the second optical coupler 22. 7, the same reference numerals as those in FIG. 3 indicate the same elements. Then, strong DC light P of, for example, about 50 mW and having a wavelength of 1.555 μm is incident on the semiconductor optical amplifier 21 through the DC light propagation optical fiber 23, thereby causing gain saturation in the semiconductor optical amplifier 21 and controlling light pulses. No fluctuation in gain due to the incidence of P _c occurs.

[0041] In this situation, when the incident control light pulse P _c and 1.56μm signal optical pulse train P _s of 1.545μm in the semiconductor optical amplifier 21, only the four-wave mixing when there is a control pulse P _c Effect occurs, the wavelength 1.5401
The phase conjugate optical pulse _Pr1 having an angular frequency of μm is emitted from the semiconductor optical amplifier 21. Incidentally, the angular frequency of the control pulse P _c and omega _p, the angular frequency of the DC light P omega _c
And the angular frequency of the signal light pulse train P _s is ω _s ,
Angular frequency of the phase conjugate light, the _{ω p + ω c + ω s} . (Fifth Embodiment) The structure adopting a structure in which DC light is incident on a semiconductor optical amplifier is not limited to a structure in which a DC light source is provided outside as shown in FIG. As shown in FIG. 8, a specific wavelength is returned from the semiconductor optical amplifier 21 in the optical separation optical circuit _An in the second and subsequent stages to return the semiconductor light in the first stage optical separation optical circuit A ₁ . A structure that returns to the amplifier 21 may be adopted.

[0042] In FIG. 8, the output end of the semiconductor optical amplifier 21 of the second and subsequent stages of the light separation optical circuit A _n optical distributor 24 for distributing the light into two is provided, the light distributor 24
Connected feedback optical fiber 25 is connected to the input side of the semiconductor optical amplifier 21 of the first stage optical separation optical circuit A ₁ in. In the middle of the feedback optical fiber 25, AS
Wavelength of E (amplified spontaneous emission) 1.
Optical filter 26 for obtaining only 555 μm light
And a directional optical isolator 27 for returning the light to the first semiconductor optical amplifier 21 are connected in series.

According to this, it is not necessary to make strong DC light incident from the outside. In FIG. 8, the same reference numerals as those in FIG. 3 indicate the same elements. Structure described in (Sixth Embodiment) The fourth and fifth embodiments adopt a structure for inputting the direct current light into the semiconductor optical amplifier 21 of the first stage optical separation optical circuit A ₁ However, if a simpler device configuration is desired, a DFB semiconductor laser may be used as the semiconductor optical amplifier.

[0044] That is, as shown in FIG. 9, DFB semiconductor laser 28 to the optical fiber 20 connecting the optical coupler 2,10 wavelength router 5,12 light separation optical circuit A _n of each stage as four-wave mixing element Is adopted, a strong DC light is automatically supplied to the DFB semiconductor laser 28, so that the gain does not fluctuate due to the incidence of the control light pulse _Pc .

For example, a control light pulse P of 1.545 μm
When using a signal optical pulse train P _{s c} and 1.56μm, the oscillation wavelength is adopted DFB semiconductor laser 28 of 1.555Myuemu. In FIG. 8, the same reference numerals as those in FIG. 3 indicate the same elements.

[0046]

As described above, according to the present invention, an excitation light pulse and a signal light pulse train are made incident on a four-wave mixing element to generate phase conjugate light, and the phase conjugate light is selectively extracted to obtain a signal. The excitation light pulse is detected as part of the signal light pulse of the light pulse train, and the excitation light pulse and the signal light pulse train output from the four-wave mixing element are made incident on the next four-wave mixing element. In this case, a time difference is provided by an integral multiple of the light pulse interval.

Since the excitation light pulse and the signal light pulse train passing through the four-wave mixing device pass through the device as they are even after the phase conjugate light is generated, it is necessary to suppress a decrease in light intensity. Can be. Also, the propagation time of the excitation light pulse with respect to the signal light pulse train is adjusted by delay means, and they are incident on the next four-wave mixing element, and the four-wave mixing element generates phase conjugate light. It becomes easy to synchronize the signal light pulse to be detected and the excitation light pulse in the pulse train, and the efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus showing a conventional technique.

FIG. 2 is a block diagram illustrating an optical time division multiplexing / demultiplexing apparatus according to an embodiment of the present invention.

FIG. 3 is a configuration diagram illustrating a circuit configuration of the optical time division multiplexing / demultiplexing device according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating wavelengths of a control pulse, a signal light pulse train, and a phase conjugate light pulse according to the first embodiment of the present invention.

FIG. 5 is a configuration diagram illustrating an optical time division multiplexing / demultiplexing apparatus according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram illustrating an optical time division multiplexing / demultiplexing device according to a third embodiment of the present invention.

FIG. 7 is a configuration diagram illustrating an optical time division multiplexing / demultiplexing device according to a fourth embodiment of the present invention.

FIG. 8 is a configuration diagram illustrating an optical time division multiplexing / demultiplexing apparatus according to a fifth embodiment of the present invention.

FIG. 9 is a configuration diagram illustrating an optical time division multiplexing / demultiplexing apparatus according to a sixth embodiment of the present invention.

[Explanation of symbols]

A ₁ to A _n ... light separating optical circuit, 1 ... signal transmission optical fiber, 2 ... control light transmission optical fiber, 3 ... optical coupler, 4 ...
Dispersion shift fiber, 5 ... wavelength router, 6-8 optical fiber, 9 ... optical receiver, 10 ... optical coupler, 11 ... dispersion shift fiber, 12 ... wavelength router, 13-15 optical fiber,
16: optical receiver, 18-20: optical fiber, 21: semiconductor optical amplifier, 22 optical coupler, 23: optical fiber for direct-current light propagation, 24: optical distributor, 25: optical fiber for feedback, 26
... optical filter, 27 ... optical isolator, 28 ... DFB semiconductor laser.

Claims (5)

[Claims] 1. A four-wave mixing device for generating a phase conjugate light by injecting an excitation light pulse and a signal light pulse train; a phase conjugate light separation means for selectively extracting the phase conjugate light; Pumping light pulse delay means for injecting the outputted pumping light pulse and the signal light pulse train and emitting the pumping light pulse with a time difference of an integral multiple of the signal light pulse interval in the signal light pulse train. An optical time division multiplexing / demultiplexing device. 2. The apparatus according to claim 1, wherein said signal light pulse train is an n (n is an integer) multiplexed light pulse train, and said n number of said four-wave mixing elements are connected in series. An optical time-division multiplexing / demultiplexing device as described in the above. 3. The optical time-division multiplexing / demultiplexing apparatus according to claim 1, wherein said four-wave mixing element is constituted by a semiconductor optical amplifier. 4. The pumping light pulse and the signal light pulse train have different wavelengths, and a DC light incident means having a higher intensity than the pumping light pulse and the signal light pulse train is attached to an incident end of the semiconductor amplifier. The optical time-division multiplexing / demultiplexing device according to claim 3, wherein: 5. The four-wave mixing element is connected in series, and a part of the output light of the four-wave mixing element at the last stage is connected to the first-stage four-wave mixing element via an optical filter. 4. The optical time-division multiplexing / demultiplexing device according to claim 3, further comprising an optical feedback unit for returning to an input terminal.