JP3201564B2 - Optical multiplexing circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical multiplexing circuit for converting a plurality of digital signals into one high-speed optical digital signal.

[0002]

2. Description of the Related Art A conventional optical multiplexing circuit multiplexes a plurality of low-speed digital signals at the stage of an electric signal, and converts the multiplexed signal into a high-speed optical digital signal by performing electric / optical conversion. That is, in this configuration, the signal speed of the multiplexed electric signal becomes the signal speed of the optical digital signal. However, since it is difficult to realize a signal speed exceeding 10 Gb / s by multiplexing electric signals, the high speed of optical signals cannot be fully utilized.

In view of this, an optical multiplexing circuit has been proposed which modulates a short optical pulse train with a plurality of digital signals and arranges them densely on a time axis to generate an ultra-high-speed optical digital signal exceeding 100 Gb / s. . FIG. 8 shows a configuration example of a conventional optical multiplexing circuit using optical short pulses. In the figure, an optical short pulse light source 61 outputs an optical short pulse train a.
At present, an optical short pulse train with a pulse width of about several picoseconds can be obtained relatively easily by using gain switching or mode locking of a semiconductor laser. This short optical pulse train a is branched by the optical branching circuit 62 and is input to the optical modulators 63-1 to 63-4, respectively. Each of the optical modulators 63-1 to 63-4 modulates the intensity of the input light with the transmission signals b1 to b4. Each signal light c1 to c4 after intensity modulation
Are delay circuits 64- so as not to overlap each other on the time axis.
Different delays are given to the signals 1 to 64-4, and the signals are multiplexed by the optical multiplexing circuit 65 and output as the multiplexed signal light d.

In such an optical multiplexing circuit, by combining an optical short pulse train and a delay circuit and multiplexing the optical signal as it is, ultra-high-speed multiplexing, which is difficult in an electric circuit, is possible.

[0005]

In a conventional optical multiplexing circuit, optical fibers are used as the optical branching circuit 62, the delay circuit 64, and the optical multiplexing circuit 65. In an optical fiber, the effective waveguide length slightly changes depending on the surrounding environment such as temperature and pressure. Therefore, the conventional circuit has a problem in that time fluctuation of an optical short pulse train occurs. To solve this problem,
It has been proposed that all circuits other than the optical short pulse light source shown in FIG. 8 be monolithically integrated on the same substrate so as to be less affected by the surrounding environment. In that case, the plurality of optical modulators 63 are also densely arranged.

By the way, when the optical modulators 63 are densely arranged, a plurality of electric signal wirings also come close to each other, and there is a problem that mutual interference between the wirings increases. Further, each delay circuit 6
The delay amount added in 4 is a fixed value determined by the length of the optical waveguide, and there is a problem that the delay amount cannot be adapted to the change in the repetition period of the optical short pulse train. SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical multiplexing circuit that can handle ultra-high-speed optical signals and has excellent controllability.

[0007]

SUMMARY OF THE INVENTION An optical multiplexing circuit according to the present invention converts a plurality of transmission digital signals into signal lights having different wavelengths, and multiplexes and outputs each signal light. A waveform shaping circuit that takes the intensity product of the signal light and the optical short pulse train, converts the wavelength-multiplexed signal light into an optical short pulse, and outputs the resulting signal.
A phase modulation means for giving a linear frequency displacement,
A dispersion circuit that receives the wavelength multiplexed signal light output from the tuning means and outputs a time multiplexed signal light that is spread on a time axis by adding a different delay according to the wavelength, and a time multiplexed signal light and a predetermined wavelength. A wavelength conversion circuit for calculating an intensity product with the continuous light or the optical short pulse train, converting the wavelength of the time-multiplexed signal light into a predetermined wavelength, and outputting the converted signal.

The waveform shaping circuit includes a two-input two-output optical coupler having a one-to-one branching ratio in a predetermined wavelength region, and two output ports of the optical coupler having a flat dispersion characteristic in a predetermined wavelength region. An optical fiber loop connecting between
Means for inputting an optical short pulse train having a wavelength within a predetermined wavelength range to the optical fiber loop so as to propagate in the optical fiber loop in only one direction; Means for inputting to the input port;
Of the light output from the other input port of the optical coupler,
Means for transmitting only the wavelength of the wavelength multiplexed signal light ( claim 2 ).

[0009] The waveform shaping circuit receives an optical short pulse train and a wavelength multiplexed signal light, and outputs a nonlinear reflected light having an intensity product thereof, which has a saturable absorption characteristic. and means for transmitting only the wavelength of light (claim 3). The wavelength conversion circuit has a two-input two-output optical coupler having a one-to-one branching ratio in a predetermined wavelength region, and a flat dispersion characteristic in a predetermined wavelength region;
An optical fiber loop connecting between two output ports of the optical coupler; a means for inputting the time-multiplexed signal light output from the dispersion circuit to the optical fiber loop so as to propagate in the optical fiber loop in only one direction; Means for inputting a continuous light or an optical short pulse train having a wavelength within the wavelength range to one input port of the optical coupler, and of the light output from the other input port of the optical coupler, and means for transmitting only the wavelength (claim 4).

The wavelength conversion circuit receives the time multiplexed signal light output from the dispersion circuit, broadens the optical spectrum and outputs the optical fiber, and means for transmitting a predetermined wavelength component from the signal light having the broadened optical spectrum. ( Claim
5 ). Further, the optical multiplexing circuit of the present invention can
Multiple continuous lights with different wavelengths from each other
Digital signals, each having a different wavelength.
A plurality of external modulators that convert the
Means for wavelength-multiplexing and outputting signal light , and wavelength-multiplexed signal light
And the intensity product of the light short pulse train input from outside and
Waveform shaping circuit that converts WDM signal light into short optical pulses and outputs them
Input a wavelength-division multiplexed signal light,
Add different delays depending on
Circuit that outputs time-multiplexed signal light, and time-multiplexed signal
Intensity product of light and continuous light of specified wavelength input from outside
And convert the wavelength of the time multiplexed signal light to a predetermined wavelength.
Multiple units consisting of output wavelength conversion circuits
Input to multiple external modulators of each unit.
And a light source that outputs continuous light with different wavelengths
Outputs continuous light of a predetermined wavelength to be input to the wavelength conversion circuit
The light source is shared between the units, and the wavelength conversion
The configuration is such that continuous light beams with different wavelengths are input to the path.
Short pulse train input to the waveform shaping circuit of each unit
For sharing the short pulse light source that outputs light between units
And wavelength multiplexing the output light of the wavelength conversion circuit of each unit.
And output the result (claim 6).

[0011]

In the optical multiplexing circuit according to the present invention, a plurality of transmission signal lights are wavelength-multiplexed, and the wavelength-multiplexed signal light and the optical short pulse train are input to the waveform shaping circuit, whereby the waveform is shaped by the optical short pulse train. Wavelength multiplexed signal light is generated. In the dispersion circuit that inputs the wavelength-division multiplexed signal light that has been made into an optical short pulse,
Using the wavelength dependence of the group velocity delay, a different delay is added to each short optical pulse of each wavelength. As a result, time-multiplexed signal light spread on the time axis according to the wavelength is generated. The time-multiplexed signal light is input to the wavelength conversion circuit, and each wavelength component is converted into a predetermined wavelength, whereby a multiplexed signal light having a uniform wavelength can be generated.

Further, a linear chirp is given to each optical short pulse by performing phase modulation on the wavelength multiplexed signal light which has been optically shortened by the phase modulating means. As a result, it is possible to suppress the spread of the pulse width generated in the dispersion circuit, and to generate the time-multiplexed signal light without the spread of the pulse width. A non-linear Sagnac interferometer can be used as the waveform shaping circuit and the wavelength conversion circuit ( claims 2 and 4 ). When used as a waveform shaping circuit, a wavelength multiplexed signal light and an optical short pulse train are input, and a wavelength multiplexed signal light whose waveform is shaped by the optical short pulse train is output. When used as a wavelength conversion circuit, a time multiplexed signal light and a continuous light or an optical short pulse train are input, and the wavelength of the time multiplexed signal light is converted into a continuous light or an optical short pulse train.

[0013] may be an element having a saturable absorption characteristic as a waveform shaping circuit (claim 3). In this case, the wavelength-division multiplexed signal light and the optical short pulse train are input, and the non-linearly reflected light with an AND is extracted to output the wavelength-division multiplexed signal light whose waveform is shaped by the optical short pulse train. It may be provided by an optical fiber and an optical filter as a wavelength converter (claim 5). The wavelength conversion is performed by converting the time multiplexed signal light output from the dispersion circuit into a white pulse and cutting out a predetermined wavelength.

By unitizing the optical multiplexing circuit of the present invention and sharing the light source of each unit in parallel, a large amount of information can be multiplexed on the time axis and the wavelength axis with a small number of light sources. .

[0015]

【Example】

(First Embodiment) FIG. 1 shows the configuration of an optical multiplexing circuit according to a first embodiment of the present invention. In the figure, an optical short pulse light source 11 outputs an optical short pulse train a having a wavelength λa. Light sources 12-1 to 12-1
12-5 outputs the continuous light e1 ～E5 wavelength lambda ₁ to [lambda] _5. The optical modulators 13-1 to 13-5 have wavelengths λ _{1 to} λ ₅
Are intensity-modulated by the transmission signals b1 to b5 to output signal lights f1 to f5. Waveform shaping circuit 14
The signal light f1 to f5 of the wavelength lambda ₁ to [lambda] ₅ is input into the port to wavelength multiplexing, and enter the wavelength λa of the optical short pulse train a port, the wavelength-multiplexed signal light g of the wavelength lambda ₁ to [lambda] ₅ Output. The wavelength multiplexed signal light g is divided into wavelengths λ ₁ to λ arranged on the time axis via an optical fiber 15 having a different group velocity for each wavelength.
_The signal is converted into a time multiplexed signal light h and input to the port of the wavelength conversion circuit 16. The continuous light i having the wavelength λi output from the light source 17 is input to the port of the wavelength conversion circuit 16.
The wavelength conversion circuit 16 outputs the multiplexed signal light d obtained by converting the time multiplexed signal light h having the wavelengths λ _{1 to} λ ₅ into the wavelength λi of the continuous light i.

FIG. 2 shows a time waveform and an optical spectrum waveform of the signal light of each part of the first embodiment. In the figure, the signal light f1 is (1,1,1,1,1,1,1, ...) and the signal light f2 is (0,1,0,1,1).
0,1,0, ...), the signal light f3 is (0,0,1,1,0,0,1, ...) and the signal light f4 is (0,0,0,0,1,1,1,1). …) And the signal light f5 is (1,1,1,
0,0,0,0, ...). The waveform shaping circuit 14 includes a port,
In this configuration, when light is input at the same time, the light of the port is output. Here, the wavelength multiplexed signal light g of the signal lights f1 to f5 cut out by the optical short pulse train a is output. That is, the time waveform of the wavelength multiplexed signal light g is the optical short pulse train a
The wavelength component at each time is included in each optical short pulse. A wavelength lambda ₁ to the optical short pulse at time t _1, lambda
₅ contains components, at time t ₂ wavelengths lambda _1, lambda _2, in which the component is included in the lambda _5.

When such wavelength multiplexed signal light g is input to the optical fiber 15, the group velocity differs for each wavelength.
At the output end of the optical fiber 15, the light spreads on the time axis according to the wavelength. That is, at time t ₁ ~t _2, the time t ₁ of the signal light f1
An optical short pulse train of (1,0,0,0,1) is formed according to .about.f5. At time t ₂ ~t _3, optical short pulse train to be in (1,1,0,0,1) corresponding to the signal light f1 to f5 of the time t ₂ is formed.
By optimizing the oscillation wavelengths of the light sources 12-1 to 12-5 according to the dispersion characteristics of the optical fiber 15, short optical pulses can be arranged at regular intervals on the time axis. In this way, the signal lights f1 to f5 are multiplexed on the time axis,
It becomes a time-multiplexed signal light h having components of wavelengths λ _{1 to} λ ₅ .

The wavelength conversion circuit 16 is configured to output the light of the port when the light is simultaneously input to the port, similarly to the waveform shaping circuit 14, and here, the wavelengths λ _{1 to} λ are used.
_{The 5} time-multiplexed signal light h is converted into the wavelength λi of the light source 17 and output as the multiplexed signal light d. The light source 17
The wavelength of the multiplexed signal light d can be set according to the wavelength .lambda.i.

Further, an optical short pulse train having a wavelength λi synchronized with the time multiplexed signal light h may be input to a port of the wavelength conversion circuit 16. In this case, it is possible to generate the multiplexed signal light d whose waveform has been shaped simultaneously with the wavelength conversion. As described above, the present embodiment is configured to add a different delay to each short optical pulse of each wavelength by utilizing the wavelength dependence of the group velocity delay of the optical fiber 15. Although the length of the optical fiber 15 slightly changes with respect to the surrounding environment such as temperature and pressure, the dispersion characteristics of the optical fiber are hardly affected by such a surrounding environment. Therefore, the configuration of the present embodiment can reduce the fluctuation of the delay with respect to a temperature change or the like, as compared with the case of adding the delay by changing the optical fiber length as in the related art.

In the present embodiment, the amount of additional delay is defined by the wavelength propagating in the optical fiber. Therefore, by using the variable light sources as the light sources 12-1 to 12-5, the position of the short optical pulse on the time axis can be easily controlled. That is, the optical multiplexing circuit of the present invention
Time slot conversion between time-multiplexed signals by wavelength control can be performed simultaneously.

In this embodiment, an arrangement is shown in which the dispersion of an optical fiber is used as a dispersion circuit. However, an element such as a diffraction grating pair having a different propagation time depending on the wavelength may be used. FIG. 3 shows a configuration example of a nonlinear Sagnac interferometer used as the waveform shaping circuit 14.

In the figure, the nonlinear Sagnac interferometer is
It comprises a 2 × 2 optical coupler 21, an optical fiber loop 22, an optical coupler 23, and an optical filter 24. Wavelength λ _{1 to} λ
_5, the signal lights f1 to f5 are input from the port of the 2.times.2 optical coupler 21 and separated one by one.
2 are guided in both directions. An optical short pulse train a of wavelength λa is
The light is input clockwise through the optical coupler 23 into the optical fiber loop 22. The two signal lights f1 to f5 are multiplexed again by the optical coupler 21 and interfere with each other. However, when there is no short optical pulse, the phase difference becomes zero, so that the signal returns to the input port. On the other hand, the optical short pulse train a is mainly composed of clockwise signal lights f1 to f1.
Since the phase of f5 is changed, the signal light is output from the port when the phase difference between the two signal lights becomes π under appropriate conditions. Short optical pulse train a wavelength λa that is output to the port was removed in the optical filter 24, by passing only the signal light f1 to f5 of the wavelength lambda ₁ to [lambda] _5, the wavelength which is waveform-shaped in accordance with the short optical pulse It can be converted to multiplexed signal light g.

In order to enable such conversion over a wide wavelength range, it is necessary to use an optical fiber loop 22 having a flat dispersion characteristic. As an optical fiber which satisfies such properties, an optical fiber such as a double-core fiber in which the dispersion characteristics are flattened by adjusting the waveguide dispersion is known. In addition, as the waveform shaping circuit 14, an element having a saturable absorption characteristic that outputs nonlinear reflected light obtained by taking the logical product of the optical short pulse train a and the signal lights f1 to f5 can be used (R. Tkahashi, et al., "1.55
μm Ultrafast Surface-Reflection All-optical Swit
ching Using Low-temperature-grown Be-doped Straine
d MQWs ", ECOC'94, Vol.1, pp.113-116, 1994).

On the other hand, the wavelength conversion circuit 16
In this configuration, when light is input at the same time, the light from the port is output, and a nonlinear Sagnac interferometer similar to the waveform shaping circuit 14 can be used. That is, when the optical short pulse train is input to the port, the nonlinear Sagnac interferometer functions as a waveform shaping circuit that shapes the signal light input to the port according to the optical short pulse. Also, it functions as a wavelength conversion circuit for converting the input light of the port into the wavelength of the input light of the port.

FIG. 4 shows another example of the configuration of the wavelength conversion circuit 16. In the figure, the wavelength conversion circuit 16 of this embodiment is configured using an optical amplifier 25, a dispersion flattening fiber 26, and an optical filter 27. When an optical pulse whose center wavelength is equal to the zero-dispersion wavelength of an optical fiber and whose optical power is large is input to the optical fiber, the self-phase modulation effect by the optical power of the optical pulse itself and the optical nonlinear effect such as four-wave mixing become avalanche phenomenon. Then, there is a phenomenon that the optical spectrum of the light pulse is rapidly expanded. By combining this optical spectrum spreading phenomenon with an optical filter, a wavelength conversion circuit for converting to an arbitrary wavelength can be formed. This embodiment shows a wavelength conversion circuit based on this principle.

FIG. 5 shows a time waveform and an optical spectrum waveform of the signal light of each part in FIG. The time multiplexed signal light h having the wavelengths λ _{1 to} λ ₅ is amplified by the optical amplifier 25 to an optical power sufficient to cause an optical spectrum spreading phenomenon due to an optical nonlinear effect in the optical fiber, and becomes a signal light j. This signal light j
Is input to the dispersion flattening fiber 26, the optical spectrum is greatly expanded, and becomes the signal light k at the output end. The signal light k is widely spread for all light pulses in the optical spectrum. The optical filter 27 outputs a multiplexed signal light d converted to a wavelength λm by extracting a component of a predetermined wavelength λm from the signal light k. This wavelength λm can be set to an arbitrary wavelength similarly to the wavelength λi of the light source 17 of the first embodiment.

(Second Embodiment) FIG. 6 shows the configuration of an optical multiplexing circuit according to a second embodiment of the present invention. This embodiment is characterized in that the waveform shaping circuit 14 in the configuration of the first embodiment shown in FIG.
The optical phase modulator 31 is inserted between the optical fiber 15 and the optical fiber 15. In the optical multiplexing circuit of the present invention, a different delay is added to each short optical pulse of each wavelength by using the dispersion characteristics of the optical fiber 15. At this time, the optical short pulse is affected by dispersion and its pulse width is widened. This phenomenon is well known as a major factor that limits the transmission distance when transmitting a high-speed optical signal through an optical fiber.

The optical phase modulator 31 of this embodiment applies a linear chirp to each optical short pulse by performing phase modulation on each optical short pulse. Thus, the pulse width of each optical short pulse can be controlled to be equal or less at the output end of the optical fiber according to the added chirp amount and inclination. That is, an optical multiplexing circuit having no pulse width spread can be configured.

(Third Embodiment) FIG. 7 shows the configuration of a third embodiment of the optical multiplexing circuit of the present invention. The feature of this embodiment is that the optical multiplexing circuit of the first embodiment shown in FIG. 1 except for the light sources is unitized, and a plurality of these units are connected in parallel to generate an ultra-high-speed multiplexed signal light. Where you do it.

Each of the units 41-1 to 41-4 comprises an optical modulator 13-1 to 13-4, a waveform shaping circuit 14, an optical fiber 15, and a wavelength conversion circuit 16, respectively. An optical short pulse train a output from the optical short pulse light source 11 is input to a port of the waveform shaping circuit 14 of each unit.
Continuous light e1 e4 of the wavelength lambda ₁ to [lambda] ₄ output from the light source 12-1 to 12-4, the optical modulator 13-1 for each unit
13-4. Further, the light sources 12-1 to 12-4
Are shared as a light source for supplying continuous light to the port of the wavelength conversion circuit 16 of each unit. That is, each unit 41-1 to 41-4 has a corresponding light source 12-4 to 12-1.
Supplies continuous light having wavelengths λ ₄ to λ ₁ , respectively, and becomes the converted wavelength in each unit. The outputs of the units are multiplexed and output from the output terminal 42.

The throughput of the output signal light having such a configuration is such that the number of light sources is n, the modulation speed in each optical modulator is B,
If the number of units is M, then n × B × M. For example, n
= 10, B = 10 Gb / s, and M = 10, the optical signal speed at the output end of the optical multiplexing circuit of this embodiment is 1 Tb / s. As described above, by sharing the light source among a plurality of units, a large amount of information can be multiplexed on the time axis and the wavelength axis with a small number of light sources.

[0032]

As described above, the optical multiplexing circuit of the present invention makes use of the wavelength dependence of the group velocity delay of the dispersion circuit to make each optical multiplexed signal of the optical pulsation wavelength-multiplexed signal light shorter. A different delay is added for each pulse. Thereby, it is possible to generate an ultra-high-speed signal light multiplexed on the time axis and the wavelength axis. Further, since the time position of each optical short pulse is defined by the wavelength propagating through the dispersion circuit, time slots can be switched by wavelength control.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of an optical multiplexing circuit according to the present invention.

FIG. 2 is a diagram showing a time waveform and an optical spectrum waveform of signal light of each unit of the first embodiment.

FIG. 3 is a diagram showing a configuration example of a non-linear Sagnac interferometer.

FIG. 4 is a block diagram showing another configuration example of the wavelength conversion circuit 16;

FIG. 5 is a diagram showing a time waveform and an optical spectrum waveform of signal light of each unit in FIG. 4;

FIG. 6 is a block diagram showing a configuration of an optical multiplexing circuit according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a third embodiment of the optical multiplexing circuit of the present invention.

FIG. 8 is a block diagram showing a configuration example of a conventional optical multiplexing circuit using optical short pulses.

[Explanation of symbols]

 Reference Signs List 11 light short pulse light source 12 light source 13 optical modulator 14 waveform shaping circuit 15 optical fiber 16 wavelength conversion circuit 17 light source 21 2 × 2 optical coupler 22 optical fiber loop 23 optical coupler 24 optical filter 25 optical amplifier 26 dispersion flattening fiber 27 light Filter 31 Optical phase modulator 41 Unit 61 Optical short pulse light source 62 Optical branch circuit 63 Optical modulator 64 Delay circuit 65 Optical multiplexing circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04B 10/00-10/28 H04J 14/00-14/08

Claims (6)

(57) [Claims] Means for converting a plurality of transmission digital signals into signal lights having different wavelengths, multiplexing and outputting each signal light, and obtaining an intensity product of the wavelength-multiplexed signal light and an optical short pulse train. A waveform shaping circuit that converts the wavelength-multiplexed signal light into an optical short pulse and outputs the signal;
A phase modulation unit for giving a frequency displacement, and a wavelength division multiplexed signal light output from the phase modulation unit, and a time multiplexed signal light output on a time axis extended by adding different delays depending on the wavelength. A wavelength conversion circuit that takes an intensity product of the time multiplexed signal light and a continuous light or an optical short pulse train having a predetermined wavelength, converts the wavelength of the time multiplexed signal light into a predetermined wavelength, and outputs the converted wavelength. An optical multiplexing circuit characterized by the above-mentioned. 2. The optical multiplexing circuit according to claim 1, wherein the waveform shaping circuit comprises: a two-input two-output optical coupler having a one-to-one branching ratio in a predetermined wavelength region; An optical fiber loop having a flat dispersion characteristic and connecting between two output ports of the optical coupler; and an optical short pulse train having a wavelength within the predetermined wavelength region propagates in the optical fiber loop in only one direction. Means for inputting to the optical fiber loop such that the wavelength-division multiplexed signal light which has been optically shortened is input to one input port of the optical coupler; and light output from the other input port of the optical coupler. Means for transmitting only the wavelength of the wavelength multiplexed signal light. 3. The optical multiplexing circuit according to claim 1, wherein the waveform shaping circuit inputs the optical short pulse train and the wavelength multiplexed signal light, and outputs a nonlinear reflected light having an intensity product thereof. An optical multiplexing circuit, comprising: an element having: and means for transmitting only the wavelength of the wavelength multiplexed signal light among the nonlinear reflected light. 4. The optical multiplexing circuit according to claim 1, wherein the wavelength conversion circuit comprises: a two-input two-output optical coupler having a one-to-one branching ratio in a predetermined wavelength region; An optical fiber loop having a flat dispersion characteristic and connecting between two output ports of the optical coupler; and a time multiplexed signal light output from a dispersion circuit is propagated in the optical fiber loop only in one direction. Means for inputting to the optical fiber loop, means for inputting continuous light or a short optical pulse train having a wavelength within the predetermined wavelength region to one input port of the optical coupler, and from the other input port of the optical coupler Means for transmitting only the wavelength of the continuous light or the optical short pulse train out of the outputted light. 5. The optical multiplexing circuit according to claim 1, wherein the wavelength conversion circuit receives the time multiplexed signal light output from the dispersion circuit, broadens the optical spectrum, and outputs the optical fiber. Means for transmitting a predetermined wavelength component from the signal light having a widened spectrum. 6. Different wavelengths inputted from the outside are different from each other.
Transform multiple continuous lights with multiple transmitted digital signals.
Tunable and converted to multiple signal lights with different wavelengths
Multiplexes each signal light and outputs it.
And a short optical pulse train input from outside with the wavelength multiplexed signal light.
The intensity product of the wavelength multiplexed signal light and the optical short pulse
And a waveform shaping circuit that outputs the wavelength-division multiplexed signal light that has been made into an optical short pulse.
Spread on the time axis by adding different delays according to each
A dispersion circuit that outputs a time-multiplexed signal light, and the time-multiplexed signal light and a predetermined wavelength that is input from the outside.
Determine the wavelength of the time-multiplexed signal light by taking the intensity product with the continuous light.
It is composed of a wavelength converting circuit for converting the the wavelength
And a plurality of external modulators of each unit.
A light source that outputs continuous light of different lengths,
Outputs continuous light of a predetermined wavelength to be input to the wavelength conversion circuit
The light source is shared between the units, and the wave of each unit is
A structure in which continuous lights having different wavelengths are input to the length conversion circuit.
And an optical short pulse train input to the waveform shaping circuit of each unit.
The light short pulse light source that outputs the light is shared between the units.
Configuration and and the output light of a wavelength converter of the respective units and wavelength multiplexing
An optical multiplexing circuit having a configuration for outputting .