JPH08110534A - Batch multi-channel full light wave tdm-wdm conversion circuit and batch multi-channel full light wave tdm separation circuit - Google Patents

Abstract

PURPOSE: To separate plural channels collectively without complicating constitution and making it a large scale in a TDM separation circuit. CONSTITUTION: This circuit is provided with a control light source 10 generating control light pulse lines incorporating N kinds of optical frequencies synchronizing with N channels (N is integer of 2 or above) of signal light pulse lines to be separated among multiplexed signal light pulse lines that plural channels of signal light pulse lines are time division multiplexed, an optical multiplexer 11 multiplexing the multiplexed signal light pulse lines and the control light pulse lines, a non-linear optical medium 12 inputting the output light of the optical multiplexer 11, inducing a four light waves mixture effect between N channels of signal light pulse lines and the control light pulse lines having N kinds of optical frequencies and outputting conversion light pulse lines in which N systems of light pulse lines of which optical frequencies are different from each other are mixed and an optical demultiplexer 13 spatially separating N systems of light pulse lines from the conversion light pulse lines according to respective optical frequencies.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collective multi-channel all-optical TDM that collectively separates, for each channel, a multiplexed signal light pulse train in which signal light pulse trains of a plurality of channels are temporally multiplexed in a time division multiplexing optical transmission system. (Time Division Mu
ltiplexed) -WDM (Wavelength Division Multiple)
xed) conversion circuit and batch multi-channel all-optical TDM separation circuit.

[0002]

2. Description of the Related Art FIG. 14 shows a configuration example of a conventional optical pulse separation circuit. The configuration shown in FIG. 14 is called a “nonlinear loop mirror”, and an optical Kerr medium (nonlinear optical medium) 42 is inserted in a loop connecting two ports 41b and 41c of a 2 × 2 optical coupler 41. It has been configured. Further, the optical multiplexer 4 is provided between the port 41b and the optical Kerr medium 42.
3 is inserted, and the optical demultiplexer 44 is inserted between the port 41c and the optical Kerr medium 42.

The multiple signal optical pulse train input through the optical circulator 45 is input into the port 41a of the optical coupler 41 and is divided into two equal parts, one component is clockwise from the port 41b, and the other component is the port. It is input into the loop so as to propagate counterclockwise from 41c. On the other hand, the control light pulse train is input into the loop via the optical multiplexer 43,
It propagates clockwise and is output from the optical demultiplexer 44 to the outside of the loop. At this time, the phase of the clockwise multiple signal light pulse propagating in an overlapping manner with the control light pulse changes due to the Kerr effect of the control light pulse. Therefore, the optical coupler 4
When the clockwise and counterclockwise multiplex signal optical pulses are combined again in 1, the phase of the clockwise multiplex signal optical pulse overlapping the control light pulse is the same as the phase of the counterclockwise multiplex signal optical pulse. It deviates by π. As a result, the signal light pulse train 1 overlapping the control light pulse is separated and output from the port 41d. On the other hand, the phase of the clockwise multiplex signal light pulse that does not overlap the control light pulse substantially matches the phase of the counterclockwise multiplex signal light pulse, so the signal light pulse train 2 is output from the port 41a. This signal light pulse train 2
Is output to the outside through the optical circulator 45.
In this way, only the specific channel synchronized with the control light pulse train can be separated from the multiple signal light pulse train.

Next, a conventional optical pulse separation circuit having a structure different from that shown in FIG. 14 will be described with reference to FIG. FIG. 15 shows the configuration of a conventional optical pulse separation circuit utilizing the four-wave mixing effect. The configuration shown in FIG. 15 utilizes the optical frequency conversion effect by the four-wave mixing effect in the optical fiber (PA Andrekson et al., "16").
Gb / s all-optical demultiplexing using four-wave-m
ixing ", Elect. Lett. vol.27, pp.922-924, 1991).
In this configuration, the multiplexed signal optical pulse (optical frequency νs) and the control optical pulse (optical frequency νp) are multiplexed by the optical multiplexer 51, and the third-order nonlinear optical medium (polarization maintaining optical fiber) 52
Is incident on. In the nonlinear optical medium 52, due to the four-wave mixing effect, which is one of the third-order nonlinear optical effects, the multiple signal light pulse and the control light pulse interact parametrically, and the optical frequency ν (= 2νs−νp) is converted. Light pulse,
Alternatively, a converted light pulse having an optical frequency ν '(= 2νp-νs) is generated. That is, the converted optical pulse having the optical frequencies ν and ν ′ is generated with respect to the multiple signal optical pulse that temporally overlaps with the control optical pulse. The converted optical pulse train composed of such converted optical pulses can be separated from the output of the nonlinear optical medium 52 by using the optical demultiplexer 53 or the optical filter. That is, it is possible to separate only the signal light pulse train of a specific channel synchronized with the control light pulse train from the multiple signal light pulse train.

[0005]

The conventional optical pulse separation circuit shown in FIG. 14 can only separate a specific channel synchronized with a control optical pulse from a signal optical pulse train and other channels. Therefore, in order to completely separate the N-multiplexed channels, it is necessary to use N-1 optical pulse separation circuits, which causes a problem that the configuration becomes complicated and large-scaled.

Further, the conventional optical pulse separation circuit shown in FIG. 15 can only extract the converted optical pulse (ν, ν ') of a specific channel synchronized with the control optical pulse from the signal optical pulse train. Therefore, in order to completely separate the N-multiplexed channels, it is necessary to separate each channel by using N optical pulse separation circuits, resulting in a complicated and large-scale configuration. The present invention has been made in view of the above-mentioned circumstances, without adopting a multi-stage configuration,
Batch multi-channel all-optical TDM-WDM conversion circuit and batch multi-channel all-optical T capable of collectively and spatially separating the signal light pulses of each channel from the multi-signal optical pulse train
An object is to provide a DM separation circuit.

[0007]

In order to solve the above-mentioned problems, the present invention provides an N channel (N is 2 or more) to be separated from a multiplexed signal light pulse train in which signal light pulse trains of a plurality of channels are time-division multiplexed. (A whole number of), a control light source for generating a control light pulse train including N kinds of optical frequencies in synchronization with the signal light pulse train, an optical combining unit for combining the multiple signal light pulse train and the control light pulse train, and the optical combining unit. The output light of the wave means is input, and a four-wave mixing effect is induced between the N-channel signal light pulse train and the control light pulse train having N kinds of light frequencies, and N-system light pulse trains having different light frequencies are mixed. A nonlinear optical medium that outputs the converted optical pulse train, and an optical demultiplexing unit that spatially separates the N optical pulse trains from the converted optical pulse train according to each optical frequency are provided. It is set to (claim 1).

Further, the control light source includes N kinds of optical frequencies in synchronization with an N-channel signal light pulse train to be separated from a multiplexed signal light pulse train in which a plurality of signal light pulse trains are time-division multiplexed. The control light pulse train whose optical frequency monotonously changes in time series is generated (claim 2). Further, the control light source is synchronized with an N-channel signal light pulse train to be separated out of the multiplexed signal light pulse train in which the signal light pulse trains of a plurality of channels are time-division multiplexed, and an optical frequency is included so as to include N kinds of optical frequencies. Is configured to generate a control light pulse train having a chirping that continuously changes in time series and having a time width including an N-channel signal light pulse train (claim 3). Further, the multiplexed signal light pulse train is composed only of polarization components in the same direction as one of the two principal axes of the nonlinear optical medium, and the control light source is polarized in the same direction as the polarization component of the multiplexed signal light pulse train. It is characterized in that it is configured to generate a control light pulse train consisting of only wave components (claim 4). Further, a birefringence compensating means for compensating for a propagation group delay difference generated between the two principal axes of the nonlinear medium is provided between the optical multiplexing means and the optical demultiplexing means (claim 5).

Further, the control light source is caused to generate a control light pulse train in a polarization direction in which the conversion efficiencies of four-wave mixing by the two principal axes of the non-linear optical medium are matched, and two polarizations of the output light of the non-linear optical medium are generated. (Polarization rotation mirror that rotates components 90 degrees relative to each other and inputs again to the nonlinear optical medium)
And an optical branch for sending the output light of the optical multiplexer to the nonlinear optical medium and sending a part or all of the output light of the nonlinear optical medium to the input light from the polarization rotation mirror to the optical demultiplexer. And means are provided (Claim 6). As a result, the signal light pulse train and the control light pulse train rotate the polarized wave by 90 degrees and pass through the nonlinear optical medium twice.

A polarization beam splitter that splits the output light of the optical multiplexer into two polarization components in the principal axis direction of the nonlinear medium, and one of the two polarization components is connected to one end of the nonlinear optical medium. , The other side is rotated by 90 degrees and connected to the other end of the non-linear optical medium, respectively, and an optical connecting means for forming a loop through the non-linear optical medium, and output light of the optical multiplexer to the polarization beam splitter. And an optical branching unit for sending a part or all of the output light of the polarization beam splitter to the optical demultiplexer (claim 7).

The control light source, when a short light pulse is inputted, outputs a wide band light pulse including a light frequency of the short light pulse, and a wide band light pulse outputted from the wide band pulse generation means. An optical branching device for branching the pulse into N pulses, N optical selection delaying means for selecting different optical frequency components from the respective branched lights output from the optical branching device, delaying them by different times, and outputting the delayed optical frequency components; An optical coupler for coupling the outputs of the individual optical selection delay means is provided (claim 8).

The control light source, when a short optical pulse is input, outputs a wideband optical pulse including the optical frequency of the short optical pulse, and a wideband light output from the wideband pulse generating means. It is characterized by having a chirping means for chirping the pulse and outputting it, and a bandpass optical filter for filtering the output pulse of the chirping means (claim 9). The control light source has a non-linear dispersion medium having a normal dispersion that outputs a chirped broadband optical pulse including an optical frequency of the short optical pulse when the short optical pulse is input (claim) 10).

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In addition, the same reference numerals are given to common portions in each drawing.

(First Embodiment) FIG. 1 shows the configuration of a collective multi-channel all-optical TDM separation circuit according to a first embodiment of the present invention. In this embodiment, a separation circuit that collectively separates four channels will be described. In FIG. 1, a time-division-multiplexed multiplexed signal optical pulse train (optical frequency νs) and a control optical pulse train having four types of optical frequencies (optical frequency νpi,
i = 1, 2, 3, 4) is multiplexed by the optical multiplexer 11 so that the corresponding optical pulses are temporally overlapped, and is incident on the nonlinear optical medium 12. The control light pulse train repeats a cycle in which the optical frequency discretely increases or decreases monotonically, and is output from the control light source 10 in synchronization with the multiple signal light pulse train. In the nonlinear optical medium 12,
A four-wave mixing effect is induced between the multiple signal light pulse and the control light pulse, and its output is a one-input multi-output type optical demultiplexer 13
Is demultiplexed for each optical frequency.

As the nonlinear optical medium 12, a polarization maintaining optical fiber, a semiconductor nonlinear material such as a semiconductor laser amplifier, an organic nonlinear material, or the like can be used. Here, an example of optical frequency conversion by the four-wave mixing effect of the present embodiment will be described with reference to FIGS. 2 (a) and 2 (b). Figure 2
FIG. 2A shows a case where the optical frequency νpi of the control optical pulse train is higher than the optical frequency νs of the multiple signal optical pulse train.
(B) shows the opposite case.

Multiple signal optical pulse train (optical frequency νs) and control optical pulse train (optical frequency νpi, i = 1, 2, 3, 4)
Are synchronized at each time slot t1, t2, t3, t4. Therefore, the signal light pulse of each channel induces the control light pulse of different light frequency and the four-wave mixing effect, and the converted light pulse train A of light frequency νi (= 2νs −νpi) or the light frequency νi ′ (= 2νpi− A converted optical pulse train B of νs) is generated. Converted light pulse train A has 4
This is a case where the multiple signal light pulse of the optical frequency νs is degenerated in the light wave mixing. Converted light pulse train B has 4
This is a case where the control light pulse of the optical frequency νpi is degenerated in the light wave mixing. When a polarization-maintaining optical fiber is used as the nonlinear optical medium 12, the converted optical pulse train A or the converted optical pulse train A or the converted optical pulse train is obtained by matching the zero-dispersion wavelength with the central wavelength of the multiplexed signal optical pulse train or the control optical pulse train that is degenerate light. The generation efficiency of the pulse train B can be maximized. On the other hand, when a semiconductor laser amplifier having an AR (non-reflection) coating on the entrance / exit surface is used as the nonlinear optical medium 12, the above-mentioned adjustment is not necessary because the phase matching condition is satisfied not only for the zero dispersion wavelength proximity. Is.

By demultiplexing the converted optical pulse train A or the converted optical pulse train B for each optical frequency, four channels can be separated at once. In the configuration utilizing the four-wave mixing effect, the multiplex signal optical pulse train having the optical frequency νs is also output, so that the multiplex optical signal pulse train can be demultiplexed by the optical demultiplexer 13. Therefore, this circuit can be connected in multiple stages, and the signal light pulse of the channel which has not been separated in the preceding stage can be separated by using the multiplexed signal light pulse trains output respectively. Further, it is possible to repeatedly read out any channel. Furthermore, the optical frequency ν
The control light pulse train of p1, νp2, νp3, and νp4 can also be demultiplexed for each optical frequency.

The optical demultiplexer 13 is shown in FIGS.
As shown in (b), a reflection type diffraction grating 14 or an arrayed waveguide type demultiplexer 15 can be used. The arrayed waveguide demultiplexer 15 includes an input waveguide 16, an input side concave slab waveguide 17, an arrayed waveguide (adjacent waveguides have an optical path length difference of ΔL) 18, an output side concave slab waveguide. 19, an output waveguide array 20. The light distributed from the input waveguide 16 to the arrayed waveguide 18 via the input side concave slab waveguide 17 has a different phase state after passing through the arrayed waveguide 18 due to the difference in optical frequency, and thus the output side concave slab waveguide. The convergence position at 19 differs depending on the optical frequency. Therefore, light of different optical frequencies is extracted into each waveguide of the output waveguide array 20 and functions as an optical demultiplexer (H. Takahashi,
Y.Hibino, I.Nishi, "Polarization-insensitive arrayed
-waveguide grating wavelength multiplexer on silic
on ", Optics Lett., vol. 17, pp. 499-501, 1992).

Here, a method of generating a multi-wavelength control light pulse,
That is, the configuration of the control light source 10 will be described. In the generation method shown in FIG. 4, a broadband white pulse generating optical fiber 21, a 1: N optical branching device 22, N wavelength selecting means 23-1 to 23-N, and N-1 optical delay means. 24-1 ~
24- (N-1) and the optical coupler 25 are used. A short optical pulse (optical frequency ν
When 0) is incident, a broadband white pulse (center optical frequency ν 0) is generated. For example, when a short optical pulse of several picoseconds having a peak power of 2 to 3 W is incident on the white pulse generating optical fiber 21 having a length of 2 to 3 km, a white pulse having a spectral width of about 200 nm or more is generated. The white pulse generated here is branched into N by the optical branching device 22, and the branched optical pulse is input to each wavelength selecting means 23-1 to 23-N.

The wavelength selecting means 23-1 to 23-N transmit and output only the optical pulses of different specific optical frequencies, and the optical delaying means 24-1 to 24- (N-1) transmit the transmitted optical pulses. Are delayed by different times. In addition, in FIG. 4, an N-th delay unit may be provided to delay all transmitted light pulses. The transmitted light pulses are combined by the optical combiner 25 to obtain the multi-wavelength control light pulse train used in this embodiment.

In the above example, the white pulse generating optical fiber 21 is used, but the invention is not limited to this as long as it can generate a white pulse. Further, the control light pulse train described above does not need to monotonically increase and monotonically decrease, and for example, FIG.
As shown in (b), the optical frequency of each optical pulse within one cycle may be different. That is, by collectively setting the transmission frequencies of the wavelength selecting means 23-1 to 23-N, a batch multi-channel all-optical system for converting a time division multiplexed optical pulse train into a wavelength multiplexed optical pulse train composed of optical pulse trains of arbitrary wavelengths. A TDM-WDM conversion circuit can be realized. 5A shows the case where the optical frequency νpi of the control light pulse train is higher than the optical frequency νs of the multiple signal light pulse train, and FIG. 5B shows the opposite case. As is clear from the above, the collective multi-channel all-optical TDM-
The configuration of the WDM conversion circuit is the same as that of the batch multi-channel all-optical TDM demultiplexing circuit, and therefore the following description will be made only for the batch multi-channel all-optical TDM demultiplexing circuit.

(Second Embodiment) FIG. 6 shows the configuration of a collective multi-channel all-optical TDM separation circuit according to a second embodiment of the present invention. In this embodiment, a configuration in which four channels are separated at once will be described. The configuration of this embodiment is the same as that of the first embodiment except for the control light source 26.
6, an optical multiplexer 11, a nonlinear optical medium 12, and an optical demultiplexer 13. In the first embodiment, when the four channels are collectively separated from the multiple signal light pulse train, the control light source 10 generates a control light pulse train having optical frequencies νp1, νp2, νp3, and νp4, and uses this. In the present embodiment, there is chirping in which the optical frequency changes substantially linearly with time at the central optical frequency νp, and four channels (t1,
Time width Δt including the signal light pulse train of t2, t3, t4)
A control light pulse having the following is generated from the control light source 26 and used. Generally, assuming that the bit rate of the multiplexed signal light pulse is B and the number of channels to be collectively separated is N, Δt>
N / B. This control light pulse has an optical frequency component νp
(T1), νp (t2), νp (t3), and νp (t4). Note that νp (t1) indicates the instantaneous optical frequency at time t1.

Here, FIG. 7A and FIG. 7 show an example of optical frequency conversion by the four-wave mixing effect of this embodiment.
This will be described with reference to (b). 7A shows the case where the central optical frequency ν p of the control optical pulse is higher than the optical frequency ν s of the multiple signal optical pulse train, and FIG. 7B shows the opposite case.

A multi-signal optical pulse train (optical frequency νs),
The optical frequency component ν p (ti) of the control light pulse is synchronized at each time slot t1, t2, t3, t4 (i =
1, 2, 3, 4). Therefore, the signal light pulse of each channel induces the control light pulse of different light frequency and the four-wave mixing effect, and when i = 1, 2, 3, 4, the light frequency νi (= 2νs−νp (ti)) Or a converted optical pulse train B having an optical frequency νi ′ (= 2νp (ti) −νs). The converted optical pulse train A or the converted optical pulse train B has an optical frequency νs in four-wave mixing.
This is a case where the signal light pulse of or the control light pulse of the central light frequency ν p is degenerated. When a polarization-maintaining optical fiber is used as the nonlinear optical medium 12, the converted optical pulse train A or the converted optical pulse train A or The generation efficiency of the optical pulse train B can be maximized. By demultiplexing the converted optical pulse train A or the converted optical pulse train B for each optical frequency,
The four channels can be separated at once.

The optical frequency νs is the same as in the first embodiment.
Since the multiplexed signal light pulse train of 1 can also be separated, this circuit can be connected in multiple stages and the signal light pulse trains that have not been separated in the previous stage can be separated by using the signal light pulse trains that are output respectively. Further, it is possible to repeatedly read out any channel.

Here, a method of generating a control light pulse having linear chirping, that is, a configuration of the control light source 26 will be described. In the first generation method shown in FIG. 8, the white pulse generating optical fiber 27 and the chirp adjusting optical fiber 2 are used.
8. A variable wavelength bandpass optical filter 29 is used. A short optical pulse (optical frequency ν
When 0) is incident, a broadband white pulse (center optical frequency ν 0) is generated as in the case described above.

The wavelength tunable bandpass optical filter 29 has a rectangular spectral transmission function, and filters the white pulse input through the chirp adjusting optical fiber 28 to obtain a control optical pulse having a wide time width and linear chirping. Is output. Also, by changing the central transmission wavelength within the white pulse wavelength range, it is possible to generate a control light pulse having linear chirping at an arbitrary optical frequency. The chirp adjusting fiber 28 adjusts the absolute value and sign of chirping according to its dispersion characteristic.

In the second generation method shown in FIG. 9, the ordinary dispersion (or
An ordinary dispersion optical fiber 30 having a dinary dispersion is used. When a short optical pulse (optical frequency ν0) is incident on the ordinary dispersion optical fiber 30, a control optical pulse having a wide time width and linear chirping is generated due to the self-phase modulation effect and the combined effect of dispersion. This is the same principle as the pulse compression method for optical pulses. (GPAgrawal, "Nonlinear
Fiber Optics ", chapter 6, Academic Press, 1989).

However, in order to obtain a spectrum width of 200 nm using the 1 km ordinary dispersion optical fiber 30, a short optical pulse having a peak power of about 200 to 300 W and a pulse width ps is required, and a white pulse is used. Than about 1
A pump power of 00 times is required. Note that the inclination of chirping is usually blue shift (the leading edge of the pulse shifts to the long wavelength side and the trailing edge shifts to the short wavelength side), and when redshift (reverse to blue shift) chirping is required, Further, the dispersion is controlled by using an optical fiber having anomalous dispersion. Even in this generation method,
By changing the central transmission wavelength of the tunable bandpass optical filter in the generated wavelength range, it is possible to generate a control light pulse having linear chirping at an arbitrary optical frequency.

By the way, in the first and second embodiments, it is premised that the polarization directions of the multiplexed signal light pulse and the control light pulse coincide with the principal axis of the nonlinear optical medium 12, but the multiplexed signal If the polarization state of the optical pulse is not fixed, proceed as follows. First, the nonlinear optical medium 1
As 2, the polarization efficiency of the four-wave mixing is small, and its polarization dispersion is so small that it can be ignored compared to the bit rate of the extracted signal. Further, the polarization of the control light pulse is set so that the intensities of the nonlinear optical medium 12 in the two principal axis directions are equal. That is, the principal axis of the nonlinear optical medium 12 and the principal axis of the polarization of the control light pulse are set to 45 degrees. This enables an optical pulse demultiplexing operation that does not depend on the polarization state of the multiplexed signal optical pulse.

When a nonlinear optical medium 12 having a polarization dependence of the efficiency of four-wave mixing and polarization dispersion is used, the signal is changed by the configurations shown in the third to fifth embodiments described later. Polarization independence that does not depend on the polarization state of the optical pulse can be achieved. The chirping does not have to be linear, and the optical frequency may be continuously changed.

(Third Embodiment) FIG. 10 shows a third embodiment of the present invention.
1 shows a configuration of a collective multi-channel all-optical TDM separation circuit according to an embodiment. The present embodiment shows a configuration in which four channels are separated at once. In FIG. 10, a multiplexed signal light pulse train (optical frequency νs
) And a control light pulse train (optical frequency νpi, i = 1, 2,
3, 4) are combined by the optical combiner 11 so that the optical pulses are temporally overlapped, and are incident on the nonlinear optical medium 12.
Here, the polarization of the control light pulse is set to 2 of the nonlinear optical medium 12.
It is set so that the intensities in the two principal axis directions are equal, that is, the principal axis of the nonlinear optical medium 12 and the principal axis of the polarization of the control light pulse are 45 degrees. As a result, the control light pulse has the same intensity of the polarization components in the two principal axis directions of the nonlinear optical medium 12.

The output of the nonlinear optical medium 12 is input to the birefringence compensating means 31, where the time difference of signal propagation between the two principal axes of the nonlinear optical medium 12 is compensated. In this embodiment, the control light pulse is degenerate light of four-wave mixing. In this case, the conversion efficiency is determined by the control light intensity in each polarization direction, the loss in the nonlinear optical medium, the nonlinear refractive index, and the phase matching amount, and when these are almost equal in the two principal axis directions, the polarization state of the signal light pulse Polarization independence that does not depend on When the nonlinear refractive index, the amount of phase matching, and the like are different for each polarization, the components of the control light in each polarization direction may be adjusted so that the conversion efficiency becomes the same. Specifically, the angle between the polarization axis of the control light entering the polarization beam splitter 33 and the main axis of the polarization beam splitter 33 may be finely adjusted from 45 degrees. The output of the birefringence compensating means 31 is 1
It is input to the input / multiple output type optical demultiplexer 13 and demultiplexed for each optical frequency. The birefringence compensating means 31 may be a substance having a linear property and capable of compensating for the delay time.

Also in this embodiment, the control light source 26 shown in FIG. 6 is used to input a control light pulse having a chirping whose optical frequency changes linearly with time and having a predetermined time width. You may do it. Further, since the birefringence compensating means 31 is a linear means, the birefringence compensating means 31 is not limited to the position shown in FIG. 10 and may be provided at any position where the control light pulse train and the multiple signal light pulse train pass. Furthermore, since the multiplexed signal light pulse train having the optical frequency ν s can be separated as in the first embodiment, this signal light pulse train can be used in the subsequent circuit.

A modified example of this embodiment will be described with reference to FIG. FIG. 11 shows the configuration of a modified example of the collective multi-channel all-optical TDM separation circuit according to the fourth embodiment of the present invention. This configuration is different from that described above in that the optical multiplexer 1
1 is provided with a polarization beam splitter 33, and an optical path 3 is formed by connecting the ends of the two polarization components demultiplexed by the polarization beam splitter 33 in a loop.
2 and the nonlinear optical medium 12 on this optical path 32.
And the point where the birefringence compensating means 31 is provided and the point where the other end of the polarization beam splitter 33 is connected to the optical demultiplexer 13.

Here, the polarization axis of the control light pulse is set to 45 degrees with respect to the main axis of the polarization beam splitter 33, and the main axis of the nonlinear medium and the main axis of the polarization beam splitter optically coincide with each other. Is configured. The polarization component perpendicular to the paper surface is incident on one end of the optical path 32, and the polarization component parallel to the paper surface is incident on the other end of the optical path 32 with the same intensity. On the other hand, the signal light pulse is incident on the polarization beam splitter 33 in an arbitrary polarization state, and is incident on one end and the other end of the optical path 32, respectively, with a splitting ratio according to the polarization state. Optical path 3 above
2 is configured in a loop shape, and the light incident from one end of the optical path 32 travels clockwise and from the other end of the optical path 32,
Light incident from the other end of the optical path 32 travels counterclockwise and is output from one end of the optical path 32.

The clockwise light and the counterclockwise light incident on the optical path 32 are respectively incident on the nonlinear optical medium 12 inserted in the optical path 32, but when the control light pulse is degenerate, four-wave mixing is performed. Since the conversion efficiency of is the same for clockwise light and counterclockwise light, polarization independent operation can be realized.
At this time, since the clockwise light and the counterclockwise light propagate in different polarization axes, generally, the birefringence in the loop causes a difference in delay time between the two lights. Here, by inserting the birefringence compensating means 31 into the loop as shown in FIG. 11, it is possible to compensate for the time delay of both-direction light.

The clockwise light that has reached the polarization beam splitter 33 again is reflected, and the counterclockwise light is transmitted, and both are in the fourth state.
Is output from the port. In the above description, the nonlinear refractive index of the nonlinear optical medium that determines the conversion efficiency of four-wave mixing,
Polarization dependence of dispersion (phase mismatch), loss, etc. is ignored, but in an actual nonlinear optical medium, these are subtly different for both polarizations, so the polarization-dependent operation of the all-optical TDM separation circuit is realized. In order to do so, it is necessary to adjust the control light pulse intensities in both directions to make the conversion efficiency of four-wave mixing the same in both directions.
For this purpose, the angle between the polarization axis of the control light incident on the polarization beam splitter 33 and the main axis of the polarization beam splitter is set to 45.
It may be finely adjusted from the degree. As is clear from FIG. 11, the birefringence compensating means 16 is connected to the polarization beam splitter 3
It may be provided in the preceding stage of 3, or in all stages of the optical demultiplexer 13. By the way, in the present embodiment, by using the birefringence compensating means 31, it is possible to obtain sufficient time accuracy for the separation of the multiplexed signal light pulse train of about 100 Gbits / sec.
A configuration example for achieving higher time accuracy will be described in the fourth embodiment.

(Fourth Embodiment) FIG. 12 shows a fourth embodiment of the present invention.
1 shows a configuration of a collective multi-channel all-optical TDM separation circuit according to an embodiment. The present embodiment shows a configuration in which four channels are separated at once. In FIG. 12, a multiplexed signal light pulse train (optical frequency νs
) And a control light pulse train (optical frequency νpi, i = 1, 2,
3, 4) are combined by the optical combiner 11 so that the optical pulses are temporally overlapped, and are incident on the nonlinear optical medium 12 via the optical circulator 14. The output of the nonlinear optical medium 12 is reflected by the polarization rotation mirror 35 and is incident again, and its output is input to the 1-input multi-output type optical demultiplexer 13 via the optical circulator 14, and for each optical frequency. It is split. The polarization rotation mirror 35 includes a polarization beam splitter 33.
And a polarization maintaining optical fiber 34 in a loop shape twisted by 90 degrees
(T. Morioka et al., "Ultrafast ref
lective optical Kerr demultiplexer using polarisat
ion rotation mirror ", Elect. Lett., vol.28, no.6, p
p.521-522, 1992).

The signal light pulse (optical frequency νs) is incident on the nonlinear optical medium 12 with an arbitrary polarization, and the control optical pulse (optical frequency νpi) is incident on the nonlinear optical medium 12 with a polarization of 45 degrees with respect to the principal axis of the nonlinear optical medium 12. It As a result, the control light pulse has the same intensity of the polarization components in the two principal axis directions of the nonlinear optical medium 12. In this configuration, the signal light pulse and the control light pulse that have passed through the nonlinear optical medium 12 are polarized by the polarization rotation mirror 35.
Then, each polarized wave is rotated by exactly 90 degrees and turned back, and is incident on the nonlinear optical medium 12 again. That is, the signal light pulse and the control light pulse travel back and forth in the nonlinear optical medium 12. The polarization is rotated by 90 degrees in the forward path and the return path, that is, the polarization component in the parallel direction and the polarization component in the vertical direction are exchanged, so that the polarization dispersion is completely compensated at the output of the return path and The two polarization components of the signal light pulse and the control light pulse come to coincide in time. In this embodiment, the control light pulse is degenerate light of four-wave mixing. This makes it possible to make the polarization independent of the polarization state of the signal light pulse.

The converted optical pulse train B output from the nonlinear optical medium 12 is guided to the optical demultiplexer 13 via the optical circulator 14. In the optical demultiplexer 13, by demultiplexing the converted optical pulse train B for each optical frequency, four channels can be separated at once. Since the multiplexed signal light pulse train having the optical frequency νs can be separated as in the first embodiment, this signal light pulse train can be used in the subsequent circuit. An optical coupler may be used instead of the optical circulator 14, and a part of the output of the nonlinear optical medium 12 may be sent to the optical demultiplexer 13. Also in this embodiment, the control light source 26 shown in FIG. 6 is used,
It is possible to input a control light pulse having a chirping in which the optical frequency changes substantially linearly with time and having a predetermined time width.

(Fifth Embodiment) FIG. 13 shows the fifth embodiment of the present invention.
The structure of embodiment is shown. The present embodiment shows a configuration in which four channels are separated at once. In FIG.
A multiplexed signal light pulse train (optical frequency νs) in which signal light pulses are time-division multiplexed, and a control optical pulse train (optical frequency νpi,
i = 1, 2, 3, 4) is combined by the optical combiner 11 so that the optical pulses are temporally overlapped, and the optical circulator 14
It is incident on the polarization beam splitter 33 via. Of the two polarization outputs of the polarization beam splitter 33, one output of the non-linear optical medium 12 remains in the polarization direction in which one output is aligned with one main axis of the non-linear optical medium 12 via the polarization maintaining optical fiber 34-1. The other output (the output in the polarization direction orthogonal to one main axis of the nonlinear optical medium 12) is incident on one end and is rotated by 90 degrees via the polarization maintaining optical fiber 34-2, and the other end of the nonlinear optical medium 12 is input. Is configured to be incident on. That is, both outputs become polarized waves in the same direction when entering the nonlinear optical medium 12. As is clear from the above, the polarization beam splitter 33 and the nonlinear optical medium 1
2 are connected in a loop via polarization maintaining optical fibers 34-1 and 34-2. When the spatial optical transmission line system is used for the connection between the polarization beam splitter 33 and the nonlinear optical medium 12, the polarization is rotated by 90 degrees instead of the polarization maintaining optical fiber 34-2 which is twisted by 90 degrees. A polarization rotator is used. The output of the polarization beam splitter 33 is output via the optical circulator 14 to the one-input multi-output type optical demultiplexer 1
3 is input and demultiplexed for each optical frequency.

The multiple signal light pulse (optical frequency ν s) has an arbitrary polarization, and the control optical pulse (optical frequency ν pi) is separated by the polarization beam splitter 33 for each polarization component, and both of the nonlinear optical medium 12 are separated. The incident light is polarized with a same intensity at the input end (usually, the main axis of polarization is 45 degrees with respect to the main axis of the nonlinear optical medium 12). That is, in the polarization beam splitter 33, the control light pulse is decomposed with a light intensity of 1: 1 in two directions, clockwise and counterclockwise, and the multiple signal light pulse is decomposed at an arbitrary ratio according to its polarization state. It On the other hand, the main axis of the nonlinear optical medium 12 and the polarization maintaining optical fiber 34-
Since the main axes of 1, 34-2 are connected so that they match,
Both the clockwise and counterclockwise lights are incident on the nonlinear optical medium 12 as linearly polarized waves in the same direction.

Since the control light pulses incident on the nonlinear optical medium 12 from both directions have the same phase matching conditions, when the control light pulse is degenerate light of four-wave mixing, the conversion efficiency is the light of the control light pulse. It will depend only on strength.
Therefore, in the nonlinear optical medium 12, the optical frequency ν i ′ (= 2ν pi) for the signal light pulses incident from both directions is obtained.
The sum of the optical intensities of the converted optical pulse train B of −νs, i = 1, 2, 3, 4) is constant regardless of the polarization state of the multiple signal optical pulse train. As a result, a stable converted optical pulse train B that does not depend on the polarization of the multiplexed signal optical pulse is obtained as the output of the polarization beam splitter 33, and polarization independence is realized. The converted optical pulse train B output from the polarization beam splitter 33 passes through the optical circulator 14 and the optical demultiplexer 1
Guided by 3. The optical demultiplexer 13 demultiplexes the converted optical pulse train B for each optical frequency ν 1 ′ to ν 4 ′ so that the four channels can be separated at once.

As in the first embodiment, the optical frequency νs
Since the multiplex signal light pulse train of can also be separated, it is possible to use this multiplex signal light pulse train in the subsequent circuit. An optical coupler may be used instead of the optical circulator 14, and a part of the output of the polarization beam splitter 33 may be sent to the optical demultiplexer 13. Also in this embodiment, the control light source 26 shown in FIG. 6 is provided, and the control light pulse having the chirping in which the optical frequency changes linearly with time and having the predetermined time width can be used. .

By the way, in the embodiment described above, an example of separating four channels is shown. However, in order to collectively separate a larger number of channels at once, a control optical pulse train having a plurality of optical frequencies, or a bandwidth and a pulse. A control light pulse having a wide width may be used. Specifically, assuming that the bit rate of the multiplexed signal light is 200 Gbit / s, the bandwidth of each signal light pulse is about 1 nm, and considering the performance of the optical demultiplexer and suppression of crosstalk between channels, ,
The frequency spacing between channels after conversion should be at least about 1 nm. Therefore, for example, collective separation of 10 channels requires a band of 1 nm × 10 × 2 = 20 nm.

On the other hand, as the nonlinear optical medium, it is desirable that the efficiency of four-wave mixing does not change significantly over such a wide band. In the case of a normal polarization-maintaining optical fiber, a 3 dB band of four-wave mixing efficiency has been experimentally obtained to be about 14 nm.
It can be said that the channels can be separated at once. Also, in the case of a semiconductor laser amplifier, the 3 dB band is 26n due to four-wave mixing caused by spectral hole burning, etc.
m is obtained (K.Kikuchi et al., "Analysis o
f origin of nonlinear gain in 1.5 μm semiconducto
r active layers by highly nondegenerate four-wave
mixing ", Appl.Phys.Lett., vol.64, pp.548-550,1994),
It can be said that 12 to 13 channels can be collectively separated by using this. Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the scope of the present invention. Also included in the present invention.

[0048]

As described above, according to the present invention,
N has the same circuit scale as the conventional 1 channel separation type
The channels can be separated together. Furthermore, 2
Accurate separation can be achieved even if a nonlinear optical medium having a four-wave mixing effect with different efficiencies depending on the two principal axes is used. Also, a polarization independent circuit can be configured. Further, it is possible to generate a control light pulse train having an arbitrary pattern. Further, it is possible to easily generate a control light pulse train having linear chirping and having a predetermined time width.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a batch multi-channel all-optical TDM separation circuit according to a first embodiment of the present invention.

FIG. 2 (a) and (b) are respectively the first of the present invention.
It is a figure which shows the example of optical frequency conversion by the four-wave mixing effect in embodiment.

3A and 3B are diagrams showing a specific example of an optical demultiplexer 13 in the same embodiment.

FIG. 4 is a diagram showing a specific configuration example of a control light source 10 in the same embodiment.

5A and 5B are diagrams showing other examples of optical frequency conversion in the same embodiment.

FIG. 6 is a block diagram showing a configuration of a collective multi-channel all-optical TDM separation circuit according to a second embodiment of the present invention.

7A and 7B are diagrams showing an example of optical frequency conversion by the four-wave mixing effect in the same embodiment.

FIG. 8 is a diagram showing a specific configuration example of the control light source 26 in the same embodiment, that is, a first generation method of a control light pulse having linear chirping.

FIG. 9 is a diagram showing a second generation method of a control light pulse having linear chirping in the same embodiment.

FIG. 10 is a block diagram showing a configuration of a collective multi-channel all-optical TDM separation circuit according to a third embodiment of the present invention.

FIG. 11 is a block multi-channel all-optical TDM according to the same embodiment.
It is a block diagram which shows the other structural example of a separation circuit.

FIG. 12 is a block diagram showing a configuration of a collective multi-channel all-optical TDM separation circuit according to a fourth embodiment of the present invention.

FIG. 13 is a block diagram showing a configuration of a collective multi-channel all-optical TDM separation circuit according to a fifth embodiment of the present invention.

FIG. 14 is a block diagram showing a configuration example of a conventional TDM separation circuit.

FIG. 15 is a block diagram showing a configuration example of a conventional TDM separation circuit utilizing the four-wave mixing effect.

[Explanation of symbols]

10, 26 ... Control light source, 11 ... Optical multiplexer, 12 ... Non-linear optical medium, 13 ... Optical demultiplexer, 14 ... Reflective diffraction grating, optical circulator, 15 ... Arrayed waveguide demultiplexer, 16 ...
Input waveguide, 17 ... Input side concave slab waveguide,
Reference numeral 18 ... Array waveguide, 19 ... Output side concave slab waveguide, 20 ... Output waveguide array 21, 27 ... White pulse generating optical fiber, 22 ... Optical brancher, 231-2
3-N ... Wavelength selecting means, 24-1 to 24-N ... Optical delay means, 25 ... Optical coupler, 28 ... Chirp adjusting optical fiber, 29 ... Tunable bandpass optical filter, 30 ... Normal dispersion optical fiber, 31 ... Birefringence compensation means, 32 ... Optical path, 3
3 ... Polarization beam splitter, 34-1, 34-2 ... Polarization maintaining optical fiber, 35 ... Polarization rotating mirror.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H04J 14/02 1/00

Claims (10)

[Claims] 1. N kinds of light are synchronized with a signal light pulse train of N channels (N is an integer of 2 or more) to be separated from a multiplexed signal light pulse train in which signal light pulse trains of a plurality of channels are time-division multiplexed. A control light source for generating a control light pulse train including a frequency, an optical combining means for combining the multiplexed signal light pulse train and the control light pulse train, and an output light of the optical combining means for inputting an N-channel signal light pulse train A nonlinear optical medium that induces a four-wave mixing effect with a control light pulse train having N kinds of optical frequencies, and outputs a converted light pulse train in which N system optical pulse trains having different optical frequencies are mixed, and the converted light. A batch multi-channel all-optical TDM-WDM conversion circuit and a batch multi-channel, which are provided with optical demultiplexing means for spatially separating the N-system optical pulse train from the pulse train according to each optical frequency. All-optical TDM separation circuit. 2. The control light source includes N kinds of optical frequencies in synchronization with an N-channel signal light pulse train to be separated from a multiplexed signal light pulse train in which signal light pulse trains of a plurality of channels are time-division multiplexed. The batch multi-channel all-optical TDM-WDM conversion circuit and the batch multi-channel all-optical TDM separation circuit according to claim 1, wherein the control optical pulse train whose optical frequency monotonously changes in time series is generated. 3. The control light source includes N kinds of optical frequencies in synchronization with an N-channel signal light pulse train to be separated from a multiplexed signal light pulse train in which signal light pulse trains of a plurality of channels are time-division multiplexed. The batch multi-channel all-optical TDM-WDM conversion according to claim 1, wherein the control optical pulse train has a chirp whose optical frequency continuously changes in time series and has a time width including an N-channel signal optical pulse train. Circuit and batch multi-channel all-optical TDM separation circuit. 4. The multi-signal light pulse train is composed only of polarization components in the same direction as either one of the two principal axes of the nonlinear optical medium, and the control light source is the same as the polarization component of the multi-signal light pulse train. A collective multi-channel all-optical TDM-WDM conversion circuit and a collective multi-channel all-optical TD according to any one of claims 1 to 3, which generates a control optical pulse train consisting only of polarized components in a direction.
M separation circuit. 5. A birefringence compensating means for compensating for a propagation group delay difference generated between two principal axes of the nonlinear medium is provided between the optical multiplexing means and the optical demultiplexing means. Multichannel all-optical TDM-WDM conversion circuit and batch multichannel all-optical TD described in
M separation circuit. 6. The control light source is 2 of the nonlinear optical medium.
A control light pulse train in a polarization direction in which the conversion efficiencies of four-wave mixing on one principal axis are the same is generated, the two polarization components of the output light of the nonlinear optical medium are rotated by 90 degrees and input to the nonlinear optical medium again. And a polarization rotation mirror to output the output light of the optical multiplexer to the nonlinear optical medium,
4. The collective multi-channel according to claim 1, further comprising: an optical branching unit for sending a part or all of the output light of the nonlinear optical medium with respect to the input light from the polarization rotation mirror to an optical demultiplexer. All-optical TDM-WDM conversion circuit and batch multi-channel all-optical TDM separation circuit. 7. A polarization beam splitter that splits the output light of the optical multiplexer into two polarization components in the principal axis direction of the nonlinear optical medium; and one of the two polarization components, the nonlinear optical medium. Optical connection means for forming a loop through the non-linear optical medium by rotating the other side by 90 degrees and connecting the other end to the other end of the non-linear optical medium; 4. The collective multi-channel all-optical TDM according to claim 1, further comprising: an optical branching unit that sends the light to a beam splitter and sends a part or all of the output light of the polarization beam splitter to an optical demultiplexer.
-WDM conversion circuit and batch multi-channel all-optical TDM separation circuit. 8. The control light source, when a short optical pulse is input, outputs a wideband optical pulse including a wideband optical pulse including the optical frequency of the short optical pulse, and a wideband pulse output means outputs the wideband pulse. An optical branching device for branching the optical pulse of N into N, and N optical selecting and delaying means for selecting different optical frequency components from the respective branched lights output from the optical branching device and delaying them by different times and outputting them. 3. An all-in-one multi-channel all-optical TDM-WD according to claim 1 or 2, further comprising an optical coupler for coupling the outputs of the N optical selective delay means.
M conversion circuit and batch multi-channel all-optical TDM separation circuit. 9. The control light source, when a short optical pulse is input, outputs a wideband optical pulse including a wideband optical pulse including the optical frequency of the short optical pulse, and a wideband pulse output means outputs the wideband pulse. 4. A collective multi-channel all-optical TDM-WDM conversion circuit and a collective multi-channel device according to claim 3, further comprising a chirping means for chirping and outputting the optical pulse of the above, and a bandpass optical filter for filtering the output pulse of the chirping means. Channel all-optical TDM separation circuit. 10. The non-linear dispersion medium having a normal dispersion, wherein the control light source outputs a chirped broadband optical pulse including an optical frequency of the short optical pulse when the short optical pulse is input. A batch multi-channel all-optical TDM-WDM conversion circuit and a batch multi-channel all-optical TDM separation circuit described.