JP3455723B2 - Optical time division multiplexing optical switch - 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 time division multiplexing optical switch for switching an optical path used in an optical time division multiplexing system of 100 Gb / s or more.

[0002]

2. Description of the Related Art Due to the rapid increase in the amount of information that accompanies the spread of the Internet, it is expected that a large amount of information of several hundred giga to several terabits per second will fly through optical fibers in the backbone transmission system in the near future. In order to realize a network in which such a large amount of information flies, wavelength division multiplexing (WD)
The M) method is being developed. In the WDM system, the transmission cost per bit can be reduced by sharing the transmission line (optical fiber, optical amplifier, etc.) with a plurality of wavelength channels.

However, some nodes have no choice but to separate and process each wavelength channel, and the number of channels is required for parts, so the node cost does not decrease so much.
In addition, basically it is necessary to monitor the network for each wavelength, and absolute wavelength control that matches the wavelength grid is also required, so network management becomes difficult when the number of channels increases.

On the other hand, if an optical time division multiplexing (OTDM) system capable of collectively monitoring all multiplexed channels is realized, it is considered that the number of parts can be reduced and network management can be simplified. However, at present, it is difficult to perform node processing at a speed of 100 Gb / s or more, and parallel processing is required by arranging components for the number of channels, which has advantages over WDM in terms of cost and reliability. I couldn't put it out.

FIG. 7 is a diagram schematically showing a configuration example of an optical switch according to the prior art which branches and outputs a set of arbitrary channels from a 640 Gb / s signal optical pulse train in which m = 64 channels are time-division multiplexed. Is. Input optical fiber 2
The signal light pulse train input from 01 is output to the branch output port 203 for each channel by the 1 × 2 optical switch 202 connected in a 64-stage cascade, or to the main path 2
The process of whether to remain in 04 is performed. The optical pulse not branched even at the final stage is output to the main output port 205.

Each optical switch 202 has a control light pulse system 2
1.5625p only when control light pulse is input from 06
From the signal light pulse train of s cycle, only the optical pulse of a predetermined channel is branched to the branch output port 203 at a 10 GHz cycle. The switch speed of the branch must be fast,
The switching repetition cycle is 100 ps, and can be realized by a Mach-Zehnder interferometer type optical switch that operates differentially with a set pulse and a delayed reset pulse (for example, S. Nakamura et al., IEICETrans.El.
etron.E82-C, 1999, P.327).

However, since each channel is controlled independently at an electrically controllable speed, it is necessary to prepare m = 64 optical switches 202 and control optical pulse systems 206.
Although omitted in the figure, in reality, precise synchronization control is required for each channel, and each channel is an extremely complicated system.

Although not shown in the figure, the branch output of each channel is finally multiplexed into one output port (optical fiber) 203, so that it is output to a predetermined bit slot. It is also necessary to make complicated arrangements for adjusting the timing, equalizing the output power of each channel, and amplifying. Therefore, the configuration becomes complicated, and it is very difficult to control when the scale is increased.

[0009]

As described above, in the conventional optical switching of the optical time division multiplexing system, since the electric control system does not respond to the speed of the optical signal subjected to the optical time division multiplexing, parallel processing is required. However, the number of parts could not be reduced, the structure was complicated, and control was difficult. Therefore, it is not possible to increase the scale, reliability cannot be improved, cost cannot be reduced, and WDM
It was not practical compared to the method.

The present invention has been made in consideration of the above circumstances, and its object is to reduce the number of constituent parts,
An object of the present invention is to provide a practical optical time division multiplex optical switch that is easy to control and has excellent cost performance and reliability as compared with the WDM system.

[0011]

(Structure) In order to solve the above problems, the present invention adopts the following structure.

That is, according to the present invention, there are m channels in one frame.
Each signal is an optical time division multiplexed optical signal pulse train comprising
Switch the output optical path of the channel in units of n frames
In an optical time division multiplex optical switch used for
Longer than the bit slot period of the optical pulse train and
Means for generating an optical pulse at a predetermined cycle different from the dome length
And according to the destination information of each channel of the signal light pulse train
Modulate the corresponding light pulse to produce the original control light pulse
Means for generating and delaying the control light pulse for a predetermined time
And a control light pulse generation system, the control light pulse generation system comprising:
The original control light pulse is controlled by the specified blank of the control light pulse train.
Corresponding bit after optical time division multiplexing in the bit slot
Means for setting a slot, and the control light pulse generation system
Bit slot corresponding to the reset light pulse from
And the bit slot is set
Light from the bit slot between
A means for reproducing / circulating a pulse a predetermined number of times not exceeding n times
And at least the control light pulse and the laser light.
Depending on the set light pulse, a different frame
By updating the bit slot in the
A first control pulse train that is synchronized with the pulse train is generated.
A control light pulse loop, and the first control light pulse loop
Each bit slot of the control optical pulse train generated by the loop
Of the input signal optical pulse train depending on the
And an optical switch for switching the optical power path .

Here, the following are preferred embodiments of the present invention.

(1) Two sets of a control light pulse generation system and a first control light pulse loop are provided for one optical switch, and each set controls a different channel. That they share.

(2) First control optical pulse loop loop and the above
A second control light pulse loop , between the optical switches ,
Once every n frames, the first control light pulse loop
One frame of the control light pulse train generated while circling the loop
To the second control light pulse loop
The control light pulse circulating in the control light pulse circulation loop of 2
Switch means for updating the column
And the second control light pulse loop is switched between
The control light pulse train for one frame updated by the means n times
The control optical path is played back while playing / circulating a predetermined number of times that does not exceed
Each channel of the optical switch according to the pattern of the loose row.
The operation to switch the output optical path of the
Repeat during a cycle period .

(3) The optical switch has a structure in which a Mach-Zehnder interferometer is provided in each of two branches of the Mach-Zehnder interferometer.

(4) The optical switch utilizes the phase change based on the intersubband absorption of the nitride semiconductor.

(5) The time required for the pulse to make one revolution in the first control light pulse circulation loop is equal to the frame length of the signal light pulse train.

(6) Cutting of the signal light pulse train every n frames
The replacement unit starts from a different frame for each channel .

(Operation) In the optical time division multiplex optical switch having the above-mentioned configuration, the control optical pulse generation system outputs the original switch changeover control signal of each channel at the electrically processable signal rate depending on the presence or absence of the optical pulse. To output. This control light pulse circulates in the control light pulse circulation loop, but at this time, since it is combined with the control light pulse of the other channel arriving at a time difference, the control light pulse of each channel is time-division multiplexed. Will be done. Then, the optical switch performs an optical path switching operation of the signal light by the time-division multiplexed control light pulse train. Further, the control light pulse of each channel is updated at a predetermined cycle. Until it is updated, the signal light pulse of the same channel is output to the same light path by the control light pulse that is repeatedly used by circulating the loop.

Therefore, according to the present invention, with one set of control system,
It is possible to control the optical path of an optical time division multiplexed high-speed signal light pulse train at an electrically processable rate. In this case, since the node processing of the optical time division multiplexed signal light can be performed with a small number of parts and simple control, the cost can be reduced as compared with the conventional optical time division multiplexing method as well as the WDM method. It is possible to realize a large-capacity optical transmission system that is highly reliable and easy to control.

[0022]

DETAILED DESCRIPTION OF THE INVENTION The details of the present invention will be described below with reference to the illustrated embodiments.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
It is a figure which shows typically the main structures of the optical time division multiplexing optical switch concerning embodiment of this. The feedback control system for stabilization, the supervisory control system, and other peripheral parts are not shown.

The optical time division multiplexing optical switch of this embodiment is
Two signal light input ports 2 and 3 and two signal light output ports 4 which are hybrid-integrated in the quartz optical integrated circuit 1.
5, 2 × 2 optical switch 6 for switching the optical path between the input port and the output port, a control optical pulse loop 7 having the 2 × 2 optical switch 6 as one element, a control optical pulse input port 8, a control optical monitor output It consists of ports 9 and 10. The control light pulse loop 7 is a 2 × 2 optical switch 6
In addition, an optical coupler 1 for inputting a control light pulse from the control light pulse input port 8 to the control light pulse loop 7
1. A non-linear optical switch 12 for extracting an unnecessary control light pulse from the control light pulse loop, a semiconductor optical amplifier 1 for compensating the loop loss of the control light pulse loop
3 and an optical waveguide 14 for connecting them.

The original control light pulse is generated by selecting the light pulse train generated by the mode-locked laser 15 that is synchronously controlled by the LibNbO ₃ Mach-Zehnder type optical modulator 17 based on the electric signal from the control system 16. It This control light pulse is branched by the 1: 1 optical coupler 18, one of which is delayed by the delay line 19 and is multiplexed again by the 1: 1 optical coupler 20, and the control light input port 8, 5: 1 light is output. Control light loop 7 via coupler 11
Entered in. The original light pulse without delay is used as the set pulse, and the delayed light pulse is used as the reset pulse. The control light pulse loop 7 loops this original control light pulse until the reset pulse arrives, and repeats the control of the 2 × 2 optical switch 6.

FIG. 2 shows one element of this optical switch.
FIG. 3 is a diagram illustrating a frame structure of an optical time division multiplexed signal input to a × 2 optical switch 6 and a timing of a control optical pulse of each channel. First, the overall operation will be described with reference to FIGS. 1 and 2.

Here, the input signal light has a signal rate of 10 Gb.
/ S channels are time-division multiplexed with 64 channels 6
It is a pulse train of 40 Gb / s. However, each channel 6
Since one dummy bit is inserted for each 4-bit processing unit, the signal rate after multiplexing is 650 Gb / s.
Has become. That is, the period of the frame composed of m = 64 bit slots is about 98.46153 ps, and the period of the bit slots is about 1.538461 ps. The node processing of each channel is periodically performed every n = m + 1 = 65 frames. Therefore, the cycle of one processing unit is 6.4 ns
Where N = n × m = m (m + 1) = 4160
There are bit slots, of which 64 bits are dummy bits.

The original control light pulse is n = m + 1
= Control different channels for every 65 bits. That is, the mode-locked laser 15 has a frequency of 10 GHz (cycle 100).
ps) to generate a pulse train. Although not shown in the figure, it is assumed that the pulse generation timing is separately and precisely controlled. The control system 16 generates control electric signals of different channels sequentially in this cycle. Light modulator 17
The optical pulse train from the mode-locked laser 15 is gated by this control signal to generate a control optical pulse train.

In this case, the first signal input port 2
The optical pulse is transmitted through the optical modulator 17 when the signal light of the channel input from the above is switched to the second signal output port 5, and the optical pulse is transmitted when the signal light is output to the first signal output port 4. I will not do it. The optical delay line 19 is
It is assumed that the original control light pulse is set to give a delay of 4096 bit slots (about 6.301538 ns). Although not shown in the figure, it is assumed that the delay amount is feedback-controlled as necessary.

The control light loop 7 has one frame = 64
The optical path length is set so that the optical pulse makes one round in a bit slot (about 98.46153 ps). Assuming a silica-based optical waveguide having a refractive index of about 1.5, the loop length is less than 2 cm, and it can be integrated in an optical integrated circuit of 1 cm square. When an original control light pulse used as a set pulse is input from the optical coupler 11, 1 frame = 64 bits (about about 1 bit) until a reset pulse corresponding to this pulse is input.
98.46153 ps) copy is made at a cycle, and switching of the signal light is repeated by the 2 × 2 optical switch 6. Since the reset pulse arrives at the optical coupler 11 in synchronization with the n = 64th turn, the 65th bit slot becomes a dummy bit. No signal is present in this dummy bit. The dummy bit can be used as a guard time for switching in a lower processing system. Therefore, a total of 6 belonging to the same channel with one set pulse
The same switching will be performed for the four bit slots.

Since the optical control pulse is input to each channel, the control optical pulse circulating loop 7 has 64 optical signals at the same time.
It means that the control information for the channels is circulating. Now, at t = 0, the channel (ch) of frame # 1
If the control information of # 1 is updated, the control information of ch # 2 is updated after t = 100 ps after the 65-bit slot (the second bit of the second frame), and so on.
Control information is updated to # 3, ch # 4, ...
The control information of ch # 64 is updated at the 64th 64th bit. In frame # 65, the control information of any channel is not updated, and the control signal of ch # 1 is reset. In frame # 1 of the next cycle, ch # 1 is updated with a new control signal, and switching of 64 bits is performed again by this control signal.

Thus, according to this optical time division multiplex optical switch, the signal rate is 10 Gb / s using only one set of optical switches (mode-locked laser 15, optical integrated circuit 1, etc.).
It becomes possible to switch the optical time division multiplexed signal of x64 channels. Compared with the conventional time division multiplex optical switch that performs parallel processing for each channel, the number of parts involved in switching can be reduced to 1/64. Control system is also 1
It has a simple configuration that sequentially processes with 0 Gb / s signals, and can be easily realized. As a result, not only the conventional optical time division multiplexing system, but also WDM can be significantly reduced in cost and reliability.

The above is the description of the overall operation of the optical time division multiplexing optical switch according to the first embodiment of the present invention. Hereinafter, 2 × 2 which is an element part of the control light pulse loop 7
Configuration examples and operations of the optical switch 6 and the nonlinear optical switch 12 will be described in more detail.

FIG. 3 is a diagram showing a configuration example of the 2 × 2 optical switch 6. This switch has nonlinear optical waveguides 31, 32, 33, 3 at each branch of the dual Mach-Zehnder interferometer between the signal light input ports 2 and 3 and the output ports 4 and 5.
4 has an inserted structure.

The signal light input from the input ports 2 and 3 is branched into the optical waveguides 36 and 37 by the 1: 1 optical coupler 35, and each of them is connected to the optical waveguides 38 and 39. 40 and 41, the optical waveguide 42,
It is branched into 43,44,45. Optical waveguides 42, 43,
Non-linear optical waveguides 31, 32, 33, 3 are provided at 44, 45.
4 and phase shifters 46, 47, 48 and 49 are inserted. The optical waveguides 42 and 43 are connected to the optical waveguides 51 and 52 by a 1: 1 optical coupler 50.
And 45 are optical waveguides 54, 5 by the 1: 1 optical coupler 53.
Connected to 5. The optical waveguides 52 and 55 are coupled to the first signal light output port 4 and the second signal light output port 5 by a 1: 1 optical coupler 56.

The phase shifters 46, 47, 48 and 49 are
The light input from the optical waveguides 38, 36, 37, 39 is
It is set to output to the optical waveguides 51, 52, 54 and 55, respectively. Therefore, the signal light input ports 2 and 3
The light input from the optical waveguide 51 is always output to the signal light output port 4 or 5, and the light input from the optical waveguide 38 is output from the optical waveguide 51.
The light input from the optical waveguide 39 is output to the output port 54. Further, in the state where the control light pulse is not input, the light input from the first signal light input port 2 is input to the first output port 4 and the light input from the second signal light input port is input to the second output light 4. Is set to be output to the signal light output port 5 (bar state). The phase of the phase shifter can be controlled, for example, by utilizing the thermo-optic effect of the silica-based optical waveguide.

When a strong control light pulse is input from the optical waveguide 38, both the signal light and the control light are split by the optical coupler 40 into the optical waveguides 42 and 43 at a ratio of 1: 1. Both the nonlinear optical waveguides 31 and 32 are set so that the phase is shifted by π by the control light. Two branches 42,43
Undergo a phase shift of the same phase, so that the output destination of the optical coupler 50 is the same as when there is no control light. On the other hand, since no phase shift occurs in the nonlinear optical waveguides 33 and 34, the phase relationship between the optical waveguides 52 and 55 in the coupler 56 is reversed, and the signal light input from the first signal light input port 2 is the second signal. The signal light input from the second signal light input port 3 to the optical output port 5 receives the signal light from the first signal light output port 4
Is output to (cross state).

Therefore, the 2 × 2 switching operation for the signal light is realized depending on the presence or absence of the control light pulse. Similarly, when a control light pulse is input from the control light input port 39, the cross state is set. If control light pulses are simultaneously input from the two control light input ports 38 and 39, both branches receive the same phase shift, resulting in a bar state. Utilizing this fact, it is possible to build an optical logic circuit.

As a non-linear optical waveguide for realizing ultra-high-speed switching operation, here, AlGaN / GaN is used.
An optical waveguide utilizing the absorption saturation (repetition rate up to 1 Tb / s) of the intersubband transition of the multiple quantum well is used. The polarizations of the control light and the signal light are both set to be perpendicular to the substrate surface. In addition, low temperature MBE grown GaAs,
Low-temperature MBE growth Be-doped InGaAs, including Sb II
It is known that switching with a repetition period of 1 ps or less can be realized even by using spin relaxation or the like of the IV compound semiconductor, and the realizing means is not limited to the above example.

FIG. 4 is a schematic configuration diagram of the nonlinear optical switch 12 composed of an asymmetric Mach-Zehnder interferometer. Input optical waveguides 61 and 62, optical coupler 63, Mach-Zehnder interferometer branches 64 and 65, nonlinear optical waveguide 66 inserted in one branch 64, phase shifter 67 inserted in the other branch 65, optical coupler 68 , Output optical waveguide 6
It consists of 9,70. When the optical pulse having a predetermined energy is input from the input optical waveguide 61, the nonlinear optical waveguide 66 and the phase shifter 67 cause a π shift in the nonlinear optical waveguide 66, and as a result, a pulse is output from the output optical waveguide 69. Is set to.

When a reset light pulse is input from the 5: 1 optical coupler 11, a copy of the set light pulse has already circulated in the control light pulse loop 7 and therefore the nonlinear optical switch has twice the pulse energy. Will be entered. (Because the coherence is reduced by 64 rounds, no significant interference occurs due to the pulse phase.)
As a result, a phase shift of 2π occurs in the nonlinear optical waveguide 66, and the output of the optical coupler 68 is the optical waveguide 70.
(Connect to 10 in FIG. 1). Therefore, by inputting the reset pulse, the circulating optical pulse can be driven out of the control optical pulse circulating loop 7.

If the inter-subband transition of a nitride semiconductor is used for the nonlinear optical waveguide 66, it is possible to sufficiently respond to a high-speed repetitive signal of 650 Gb / s.

The present embodiment is not limited to the configuration described above, but various modifications as described below are possible.

If the optical modulator 17 is a semiconductor electro-absorption modulator (including a modulator utilizing the quantum confined Stark effect of a quantum well), it may be integrated with the mode-locked semiconductor laser 15. The light source of the control light may be a mode-locked fiber laser. If the control signal rate is low, the gain switch of the semiconductor laser can also generate pulses. Alternatively, conversely, a wide control light pulse train may be generated by direct modulation of the semiconductor laser, and this may be cut out into short pulses by an optical modulator. Processing such as pulse compression and chirp compensation is performed as necessary.

The control light pulse loop 7 may be integrated with a dispersion compensating element, a pulse compressing element, an optical filter, a temperature controller, etc. for keeping the pulse waveform, spectrum, and circulating time constant. In order to prevent crosstalk, the center wavelengths of the control light and signal light should be shifted, and the signal light output port should be equipped with an optical filter to prevent transmission of the control light wavelength and the four-wave mixing light generated in the nonlinear optical waveguide. Is preferred. Also, instead of using an optical amplifier, it is also possible to use a loop loop of a method in which an optical pulse train is generated by another mode-locked laser, and the optical pulse train is modulated by a circulating signal by an all-optical switch to recreate a duplicate of a control optical pulse train. (Instead of the optical pulse train, the control signal carried on the optical pulse train is circulating).

The output of the optical waveguide 9 can be used as a monitor for the circulating pulse and the set / reset pulse (the level is different from the circulating pulse). The output of the optical waveguide 10 can be used as a monitor for the reset operation. If these outputs are unnecessary, it is not necessary to provide an output port.

The 2 × 2 optical switch 6 may be a 1 × 2 branch switch (which outputs one input to either of two branches) or a 2 × 1 merge switch (only one input from two inputs). Selected and output). The optical switch according to this embodiment is combined with an optical delay circuit,
As an element of the optical add / drop multiplexer,
It can also be used as an element of optical cross connect.

Further, a part of the time division multiplex optical switch of this embodiment may be integrated with a part of another time division multiplex optical switch or a part or all of other devices.

The bit rate, the number of channels to be multiplexed, the number of frames in the processing cycle, the number of bits until the reset pulse is input (conversely, the number of dummy bits), etc. are also limited to the above examples. is not. In addition, redundant bits such as parity and bits for synchronization may be interleaved in the signal light.

The relationship between the number of frames n of one processing unit and the number of multiplex channels m is not limited to the example of the above embodiment. If the difference between n and m is d, the channel number updated for each frame will be shifted by d. Contrary to the above embodiment, n <m may be set. For example, when m = 64 and n = 63, the control signals are updated to ch # 1 and ch # 63 in frame # 1, ch # 62 in frame # 2, and finally ch # 2 in frame # 63. Will be updated. Further, n may be twice or more than m. For example, if m = 64, n = 1000 and the bit rate after multiplexing is 640 Gb / s, the bit length as a processing unit of each channel can be increased, and the operating speed of the control pulse is about 640 Mb / s. Can be dropped into. However, the limitation on the deterioration of the pulse in the control light pulse loop 7 and the delay control of the delay line 14 become strict.

When the number of multiplexed bits m, the signal rate, etc. are changed, the control light pulse loop length also changes. Generally, since there is a loop length suitable for integration and control, m
It is necessary to properly set the values of and n according to the purpose. For example, if the frame length is 50 ps, the loop optical path length is 15 mm, and assuming a semiconductor having a refractive index of 3, the loop length is about 5 mm. With this size, it is easy to integrate it on a semiconductor substrate.

The present embodiment can be variously modified without departing from the spirit of the present invention.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention.
It is a figure which shows typically the structure of the optical switch concerning embodiment of this. The components corresponding to those of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, two control light pulse systems 81 and 82 are connected to the 2 × 2 optical switch 6. The control light pulse systems 81 and 82 are respectively the control light generation systems 15 to 20 and the control light pulse loop 7 of the first embodiment.
And the control light input / output ports (38, 51 in FIG. 3) of the different branches of the 2 × 2 optical switch 6, respectively.
And a set of 39 and 54).

The number of multiplexed channels of signal light is m = 128, and the number of frames of processing unit is set to n = 65. Each signal channel is 10 Gb / s, and a signal rate of 1.28 Tb / s in optical time division multiplexing of 128 channels (optical pulse is 1.3 Tb because a dummy bit is inserted).
/ S is flowing). The first control light pulse system 81 controls the odd-numbered channels, and the second control light pulse system 82 controls the even-numbered channels. In frame # 1, the first control light pulse system 81 updates the control signal for ch # 1 and the second control light pulse system 82 updates the control signal for ch # 66. Hereinafter, in frame # 2, the control signal is updated while shifting by two channels for each frame, such as ch # 3 and ch # 68. Only ch # 65 is updated in frame # 33, and only ch # 64 is updated in frame # 65.

Thus, the two control light pulse systems 81,
Since the odd-numbered channel and the even-numbered channel are shared by 82, one 2 × 2 switch 6 can perform twice the signal processing as compared with the first embodiment.

Thus, according to the present embodiment, as in the case of the first embodiment, an ultrahigh-speed optical time division multiplexing optical switch can be realized. Of course, in the present embodiment as well, the first
Various modifications as described in the embodiment section of are possible.

(Third Embodiment) FIG. 6 shows a third embodiment of the present invention.
It is a figure which shows typically the structure of the optical switch concerning embodiment of this.

In the first and second embodiments, each channel starts from a different frame, but in this embodiment,
By using two pulse loops 100 and 101, all channels start from the same frame. In this configuration, the number of frames n can be an integral multiple of the number of channels m.

The optical switch of this embodiment has two signal input ports 102 and 103 and two signal output ports 10.
4, 105, 2 × 2 optical switch 106, optical waveguide 107 connecting two pulse loops 100, 101, Mach-Zehnder interferometer type optical latch switch 108, 1
09, an optical filter 110, switch trigger pulse lasers 111 and 112, optical delay lines 113 and 114, a mode-locked laser 115, a control system 116, an optical modulator 117, an optical coupler 118, a control light monitor output port 127, and the like. An optical amplifier, a delay time control system, etc. are finely incorporated in the optical pulse loop, if necessary, but the explanation is omitted here for simplification.
Reference numerals 8 and 109 denote nonlinear optical waveguides 119 and 120, respectively.
Is formed in a branch between the optical couplers 121 and 122, and the set pulse input port 123 is connected to the nonlinear optical waveguide 119 and the reset pulse input port 124 is connected to the nonlinear optical waveguide 120. For the non-linear optical waveguides 119 and 120, a non-linear phenomenon such as a semiconductor optical amplifier in which the recovery time is slower than a frame length of several hundreds ps to several ns is used.

The optical signal optical pulse input from the port 102 has 40 Gb / s signal channels m = 16 channels, which is optical time division multiplexed. The optical pulse rate bit slot period is 1.5625 ps, the frame length is 25 ps, and the number of frames n in one processing period is 256. Since the dummy bit is inserted, the control light pulse is obtained by the optical modulator 117 punching out the pulse train of the 26.5625 ps cycle generated by the mode-locking (ML) laser 115 based on the electric signal from the control system 116. To be This control light pulse train is input from the optical coupler 118 to the first pulse circulation loop 100. First channel (ch #
It is assumed that the control pulse does not exist in the pulse circulation loop 100 when the pulse of 1) is input. The mode-locked laser 115 continues to output pulses even after generating the pulse corresponding to ch # 16, but the control system 116 keeps the optical modulator 117 in the off state until the next control cycle.
The control cycle of the same channel is 6.4 ns.

The optical latch switch 108 is normally set so that the pulse goes around the optical pulse loop 100. The circulation time is 25 ps, which is the same as the frame length. As a result, similar to the operation of the control light pulse loop 7 of the first embodiment, when the control light pulse of ch # 16 is input, ch # 1 (16th round) to ch # 16.
Control light pulse up to (first round) is 25 ps per frame
It will be multiplexed in the minutes.

Optical latch switch 108, pulse laser 1
11, and the optical delay line 113 includes ch # 1 to ch # 16.
After the control light pulses up to are aligned, the set pulse arrives at the nonlinear optical waveguide 119 via the optical waveguide 123 just before the control pulse for ch # 1 arrives, and the control pulse for ch # 16 is output from the loop. After that, the timing is adjusted so that the reset pulse arrives at the nonlinear optical waveguide 120 via the optical waveguide 124. The generation period of the set pulse is 6.4 ns.

When a strong set pulse is input, the phase of the nonlinear optical waveguide 119 shifts by π, and the optical coupler 1
The output of 22 switches to the optical waveguide 107 exiting the loop. Since the non-linearity is slowly recovered, the state in which the phase is shifted by π is maintained for a while. After that, when a reset pulse delayed by a predetermined amount in the optical delay line is input, the phase of the nonlinear optical waveguide 120 is also shifted by π, so that the phase difference between the two branches becomes 0, and the output of the optical coupler 122 is output. Switches to the loop again. In this way, the optical latch switch 10
Reference numeral 8 has a function of outputting the circulating pulse train to the optical waveguide 107 only from the input of the set pulse to the manual input of the reset pulse. Since the wavelength of the set / reset pulse is different from that of the control light pulse, the optical filter 110 can prevent propagation to the next stage.

# 1 to # 1 output to the optical waveguide 107
The control pulse trains up to 6 are input to the second pulse circulation loop 101 via the optical latch switch 109. That is, the set pulse is input immediately before the control pulse of ch # 1 arrives from the optical waveguide 107, and the reset pulse is input immediately after the control pulse of ch # 16 arrives.

The operation of the optical latch switch 109 is the same as that of the optical latch switch 108. Pulse laser 1
The pulse train from the optical waveguide 107 is taken into the loop 101 by the set pulse generated in 12 and input through the input port 123, and at the same time, the pulse train in the loop is output to the monitor output port 127 and control of all channels is performed. The data is updated. Further, when the loop 101 is closed by the reset pulse input via the optical delay line 114 and the input port 124, the control light pulse circulates in the loop 101.

The control light pulse circulating in the loop 101 controls the bar state and the cross state of the 2 × 2 optical switch 106. 6.4 until control data is updated
During ns (256 frames), the control is repeated so that the same output is obtained for the same channel.

As described above, in the present embodiment, the two pulse loops 100 and 101 are used, and the control light pulse trains are combined in advance by the loop loop 100 of the first stage. Circular loop 101 of the stage
And the switching control of the 2 × 2 optical switch 106 is performed based on the control light pulse train obtained by the loop loop 101, so that the frames can be synchronized and all channels can be started from the same frame. .

If it takes time to switch the optical latch switches 108 and 109, the bit slot period may be compressed and a guard time may be provided before and after the frame. Since the optical pulse loops 100 and 101 and the optical delay lines 113 and 114 of this embodiment are relatively short, it is possible to integrate all optical elements into a semiconductor optical integrated circuit.
Further, also in this embodiment, various modifications can be made as in the first embodiment.

[0070]

As described in detail above, according to the present invention, the control light pulse generation system, the control light pulse circulation loop, and the optical switch are configured as described in the claims, so that a simple control with a small number of parts is performed. Thus, it becomes possible to freely switch the signal light multiplexed in optical time division. Therefore, WD
An optical time-division multiplex optical switch that is lower in cost and higher in reliability than M and has excellent practicability is realized.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of an optical time division multiplexing optical switch according to a first embodiment.

FIG. 2 is a diagram for explaining the operation of the optical time division multiplexing optical switch according to the first embodiment.

FIG. 3 is a diagram schematically showing a configuration of a 2 × 2 optical switch used in the first embodiment.

FIG. 4 is a diagram schematically showing a configuration of a nonlinear optical switch used in the first embodiment.

FIG. 5 is a diagram schematically showing a configuration of an optical time division multiplexing optical switch according to a second embodiment.

FIG. 6 is a diagram schematically showing a configuration of an optical time division multiplexing optical switch according to a third embodiment.

FIG. 7 is a diagram schematically showing a configuration example of a conventional optical time division multiplexing optical switch.

[Explanation of symbols]

1 ... Optical integrated circuit 2, 3, 102, 103, 201 ... Signal light input port 4, 5, 104, 105, 203, 205 ... Signal light output port 6, 106 ... 2 × 2 optical switch 7, 100, 101 ... Control light pulse loop 8 ... Control light input port 9, 10, 127 ... Monitor output port 11, 18, 20, 35, 40, 41, 50, 53, 5
6, 63, 68, 118, 121, 122 ... Optical coupler 12 ... Non-linear optical switch 13 ... Optical amplifier 14, 36, 37, 38, 39, 42, 43, 44, 4
5,51,52,54,55,61,62,64,6
5, 69, 70, 107 ... Optical waveguide 15, 115 ... Mode-locked laser 16, 116 ... Control system 17, 117 ... Optical modulator 19, 113, 114 ... Optical delay line 31, 32, 33, 34, 66, 119 , 120 ... Nonlinear optical waveguides 46, 47, 48, 49, 67 ... Phase shifters 81, 82, 206 ... Control optical pulse systems 108, 109 ... Mach-Zehnder interferometer type optical latch switch 110 ... Optical filters 111, 112 ... Pulse lasers 202 ... 1x2 optical switch

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Claims (5)

(57) [Claims] 1. An output of each channel of a signal light pulse train in which an m-channel signal is time-division multiplexed in one frame.
An optical time division multiplex optical switch used to switch a power optical path in units of n frames , wherein an optical pulse is generated at a predetermined cycle longer than a bit slot cycle of the signal light pulse train and different from a frame length .
And the destination information of each channel of the signal light pulse train.
Therefore, the corresponding optical pulse is modulated and the original control optical
Means for generating a pulse and a predetermined time from the control light pulse
Means for producing a delayed reset light pulse
That the control light pulse generation and system, the original control light generated by the control pulse generating system
Pulse into a given empty bit slot of the control optical pulse train
Optical time division multiplexing and setting the corresponding bit slot
And a reset light pulse from the control light pulse generation system.
Means to reset the corresponding bit slot
And the bit slot is set and then reset
Until the optical pulse of the bit slot is exceeded n times
At least a means for reproducing / circulating a predetermined number of times
By the control light pulse and the reset light pulse.
Bit slot with different frames depending on the channel
Is synchronized with the signal light pulse train by being updated
Control pulse and the first control light pulse circulating loop sequence is generated, said first control optical pulse control light generated by the circulating loop
Depending on the presence or absence of an optical pulse in each bit slot of the pulse train
To switch the output optical path of the input signal light pulse train.
Optical time-division multiplexed optical switch and the optical switch, characterized by being provided with a to that. 2. A set of the control light pulse generation system and a first control light pulse circulation loop is provided for one of the optical switches.
2. The optical time division multiplexing optical switch according to claim 1, wherein a plurality of groups are provided, and each group shares control of a different channel. 3. The first control light pulse circulation loop and the
Between the optical switch and a second control light pulse circulating loop,
Once every n frames, the first control light pulse loop
One frame of the control light pulse train generated while circling the loop
To the second control light pulse loop
The control light pulse circulating in the control light pulse circulation loop of 2
Switch means for updating the column
And the second control light pulse loop is switched between
The control light pulse train for one frame updated by the means n times
The control optical path is played back while playing / circulating a predetermined number of times that does not exceed
Each channel of the optical switch according to the pattern of the loose row.
The operation to switch the output optical path of the
The optical time division multiplex optical switch according to claim 1, wherein the optical time division multiplex optical switch is repeated for a period of one cycle . 4. The time division multiplexed light according to claim 1, wherein the time required for the pulse to make one round in the first control light pulse loop is equal to the frame length of the signal light pulse train. switch. 5. The cutting of the signal light pulse train every n frames
The time division multiplexing optical switch according to claim 1 , wherein the replacement unit starts from a different frame for each channel .