JP2653015B2 - Wavelength / time division 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 switch for exchanging signals between wavelength division multiplexed and time division multiplexed input optical signals and output optical signals as they are.

[0002]

2. Description of the Related Art Optical communication using optical fibers for transmission lines
Since the optical fiber has a wide band, it is possible to transmit a large amount of information, and the optical fiber has an advantage that it does not receive induced noise. As an exchange used in this optical communication, an optical exchange capable of exchanging optical signals in an optical region is desirable. Such an optical switch includes a time-division multiplexed and wavelength-division multiplexed input signal and an output optical signal, such as a "optical switch" described in Japanese Patent Application No. 58-033069. An optical switch has been proposed which performs both of the split switching.

FIG. 2 is a diagram showing such a conventional optical switch. Means for performing time division switching on an input optical highway 201 which is time division multiplexed and n wavelength division multiplexed for each wavelength connected to an input terminal. T211; means λ212 for effecting wavelength division for each time slot whose output terminal is connected to the input terminal; and output optical highway 210 whose output terminal is time-division multiplexed to the input terminal and n-wavelength division multiplexed.
For time-division switching for each wavelength connected to the output terminal.

FIG. 3 is a time chart for explaining the operation of FIG.

In FIG. 3, 4001, 4004, 400
7, 4010 represents a time slot sequence of the time-division optical signal having the wavelength λ ₁ . Similarly, 4002, 4005, 4008, 4
Reference numeral 011 denotes a time slot sequence of the time-division optical signal having the wavelength λn. Time slot trains 4001 and 4002 correspond to optical signals on the input optical highway in FIG. 2, time slot trains 4004 and 4005 correspond to optical signals between T211 and λ212 in FIG.
7, 4008 corresponds to the optical signal between λ212 and T213 in FIG. 2, and the time slot sequence 4010, 4011 corresponds to the optical signal on the output optical highway 10 in FIG. At T211, the time slot of the input optical signal is shifted at the same wavelength, and as a result, the signal corresponding to the time slot 4003 is 4 in the output optical signal of T211.
Move to 006. At λ 212, the optical signal output from T 211 shifts the time slot aligned with the same time. As a result, in the output optical signal of λ 212, the signal corresponding to time slot 4006 moves to 4009. T
In 213, as a result of moving the time slot between signals of the same wavelength of the optical signal output from λ12, the time slot 400
The signal corresponding to 9 moves to 4012. Thus T
By taking a three-stage configuration of 211, λ212, and T213, a communication channel is formed between a signal of an arbitrary time slot of an arbitrary wavelength of an input signal and a signal of an arbitrary time slot of an arbitrary wavelength of an output optical signal. can do.

FIG. 4 is a diagram showing a specific example of the means T211 for performing time division switching for each wavelength shown in FIG. According to FIG. 4, T211 is connected to an optical demultiplexer 112 in which an input optical highway 111 time-division multiplexed and n-wavelength division multiplexed is connected to an input terminal, and n output terminals of the optical demultiplexer 112. N optical time switches 113 connected to input terminals
And an optical multiplexer 114 in which n input terminals are connected to output terminals of the n optical time switches 113, and an output optical highway 115 which is time division multiplexed and n wavelength division multiplexed is connected to an output terminal. The input optical signal is an optical demultiplexer 112.
Λ ₁ , λ _{2 to} λ _n are demultiplexed into time-division optical signals of each wavelength, and each time-division optical signal is time-division switched by n optical time switches, and the output of the optical time switch of each wavelength is optically multiplexed. The signals are multiplexed by the unit 114. In this way, the time division switching for each wavelength is performed between the input optical highway 111 and the output optical highway 115. As the optical time switch 113, for example, the optical phase conversion switch disclosed in the above-mentioned JP-A-53-2012 can be used. Japanese Patent Application Laid-Open No. 53-2012 discloses an optical delay memory in which a two-input two-output optical switch and an optical fiber delay circuit are connected in a ring, and light is circulated and stored.
An optical time switch for exchanging time slots by giving out after giving a predetermined delay is configured.

FIG. 5 is a diagram showing a specific example of means λ212 for performing wavelength division switching for each time slot shown in FIG. According to FIG. 5, λ212 shown in FIG. 2 is the optical branching unit 12 whose input terminal is connected to the input optical highway 121.
2 and n with the n outputs of the optical splitter 122 as inputs.
A number of variable wavelength selection element 123, and the n number of tunable wavelength selecting element 123, lambda ₁ to the output of each of the n number of tunable wavelength selecting element 123 and each of the input, n type lambda ₂ ... lambda _n N wavelength conversion elements 124 having unique output wavelengths
And an optical multiplexer 125 having n outputs of each of the n wavelength conversion elements 124 as inputs, and a highway 126 for output light connected to the output. The time division multiplexed optical signal of wavelengths λ ₁ , λ ₂ ... Λ _n transmitted from the input highway light 121 is branched into n by the optical branching unit 122 and input to the n variable wavelength selection elements 123. The variable wavelength selection element 123 outputs λ ₁ , λ ₂ ... Λ _n for each time slot of the time-division multiplexed optical signal.
The optical signal of one wavelength is selected from the time-division multiplexed optical signals of the wavelengths, and is output and input to the wavelength conversion element 124. Wavelength converting element 124, lambda _1, which of the n wavelengths lambda ₂ ... lambda _n 1
One is also entered, lambda _1, and outputs an optical signal of any one specific wavelength of n wavelengths lambda ₂ ... lambda _n. The outputs of the n wavelength conversion elements 124 having different wavelengths are output from an optical multiplexer 125.
And output to the output optical highway 126.

[0008] The variable wavelength selection element 123 is, for example, LiNb.
It can be constituted by an EO grating control light directional coupler in which an EO grating is applied to the light directional coupler on the O ₃ substrate. For more information on tunable wavelength selecting element with EO grating control light directional coupler e.g. Miki et al., "LiNbO ₃ guide wave optical wavelength tunable filter" 1930
Proceedings of the 6th JSAP Autumn Meeting 9P-M-9P
See 246.

FIG. 6 shows the wavelength conversion element 124 shown in FIG.
It is a figure which shows the specific example of. According to FIG. 6, in the wavelength conversion element 124 shown in FIG. 5, a 1 × 2 optical switch 1242 having an input terminal connected to an input optical highway 1241 and a first output of the optical switch 1242 are input. An output optical highway 1246 receives as input the harmonic generation element 1243, the output of the harmonic generation element 1243, the optical multiplexer 1244 to which the second output of the optical switch 1242 is input, and the output of the optical multiplexer 1244. Include an injection semiconductor laser 1245 connected to the output. Input optical highway 1
In the case of wavelength conversion in which λi is shorter than the intrinsic output wavelength λj of the injection type semiconductor laser, the optical signal having the wavelength of λi transmitted from the optical multiplexor 241 does not pass through the high frequency generating element 1243 by the optical switch 1242. It is input directly to 1244. On the other hand, in the case of wavelength conversion in which λi is longer than λj, the signal is input to the optical switch 1242, converted into an optical signal having a wavelength shorter than λj, and input to the optical multiplexer 1244. The switching of the optical switch 1242 is λi, λj
The communication path control unit stores the wavelength of the data as data. As a result, the output of the optical multiplexer 1244 becomes λ
j is an optical signal having a shorter wavelength than that of the injection type semiconductor laser 1
245 oscillates at λj, and an optical signal whose wavelength has been converted from λi to λj is sent to the output optical highway 1246. The high frequency generating element 1243 can be realized by a non-shaped optical crystal such as a LiNbO ₃ crystal. Injection type semiconductor laser 1245
Can be realized by, for example, a semiconductor laser having a planar stripe type double hetero structure. For details of the injection type semiconductor laser, refer to Kawaguchi, "Bistable oscillation of semiconductor laser", IEICE Technical Report ED81-10, PP7-13.

[0010]

In such a conventional switch handling wavelength division multiplexed and time division multiplexed optical signals, means T211, T21 for performing time division switching for each wavelength.
2 and means λ2 for performing wavelength division switching for each time slot
Since a total of 12 means are required, the required number of optical components is large, and the required hardware increases with the number of lines.

An object of the present invention is to provide an optical switch for handling a time division multiplexed and wavelength multiplexed optical signal which requires a small amount of optical components and can eliminate the required hardware.

[0012]

Means for Solving the Problems The wavelengths provided by the present invention are:
The time-division optical switch is a wavelength-division multiplexed and time-division multiplexed optical signal in which a plurality of time-division multiplexed optical signals having different wavelengths and a plurality of wavelengths are wavelength-division multiplexed are input from the input optical highway, and An optical splitter for splitting the wavelength division multiplexed and time division multiplexed optical signal from the input optical highway into a plurality of wavelength division multiplexed and time division multiplexed optical signals, and a plurality of wavelength division multiplexes from the optical splitter And a plurality of wavelength selection elements for selecting an optical signal of a specific wavelength from the time-division multiplexed optical signal, and an optical signal having a plurality of output terminals, each of which is input from the plurality of wavelength selection elements, and for each of the time slots. A plurality of write optical switches that emit light to any one of the plurality of output terminals, and a light output switch that is connected to each of the plurality of output terminals of the plurality of write optical switches and receives incident light. A plurality of output wavelength variable optical storage elements capable of outputting light and continuously outputting the outgoing light even if the incident light disappears and capable of changing the wavelength of the outgoing light by a control signal; and inputting to a plurality of input terminals. And a read-out matrix optical switch that emits each of the emitted light from the plurality of variable output wavelength optical storage elements to an output optical highway for each of the time slots.

[0013] In the wavelength / time division switch provided by the present invention, the readout matrix optical switch may include a plurality of readout light sources each of which outputs an optical signal input to a plurality of input terminals to an output terminal for each of the time slots. A switch and an optical combiner for combining optical signals from the plurality of readout optical switches and outputting an output optical highway.

[0014]

According to the present invention, by adopting such a configuration, a specific wavelength is selected from the wavelength division multiplexed and time division multiplexed optical signal, and the optical signal of the selected wavelength is subjected to wavelength conversion for each time slot. Since the switching can be performed and time slots can be exchanged, an optical signal of an arbitrary wavelength and an arbitrary time slot can be connected to an arbitrary outgoing line.

[0015]

FIG. 1 is a diagram showing an embodiment of the present invention, in which the wavelength division multiplexing is 2 and the time division multiplexing is 3.

The time-division multiplexed optical signals of wavelengths λ ₁ and λ ₂ on the input optical highway 1 are input to the wavelength selecting elements 3 and 4 via the optical splitter 2. The wavelength selection elements 3 and 4 select the optical signals of the wavelengths λ ₁ and λ ₂ from the wavelength multiplexed optical signals and send them to the write optical switches 900 and 901. The write optical switches 900 and 901 respectively transmit the signal of the first time slot to the output wavelength variable bistable elements 910 and 913 and the signal of the second time slot to the output wavelength variable bistable element 91 respectively.
1, 914 and the signal of the third time slot are sequentially transmitted to the output wavelength variable bistable elements 912 and 915, respectively. The output wavelength variable bistable elements 910 to 915 store the optical signal of each time slot and convert the wavelength into _one of λ ₁ and λ ₂ . Read optical switch 920,
The 921 and the optical coupler 15 constitute a 6 × 1 matrix optical switch. Then, the output wavelength variable bistable element 910
The optical signals stored in .about.912 and 913.about.915 are extracted by the readout optical switches 920 and 921 to the output highway 16 via the optical coupler 15 at timings corresponding to the respective time slots on the output highway 16.

FIG. 7 is a view for explaining one structure of the variable output wavelength bistable elements 910 to 915 in the embodiment of the present invention shown in FIG. In FIG. 7, the variable output wavelength bistable element is a variable output wavelength bistable semiconductor laser chip 1000.
One end face 100 of the active layer 1001 indicated by a broken line inside
2 and the other end face 1003, the incident light 1004 is input to one end face 1002 of the active layer 1001, the outgoing light 1005 is output from the same end face 1002, and the other end face 1010
03 emits another outgoing light 1006. Further, currents i ₂ and i ₃ are injected into the output wavelength tunable layer stable semiconductor laser chip 1000 through the conductors 1007 and 1008, respectively. Therefore, the output wavelength-tunable layer stabilized semiconductor laser chip 1000 the sum i ₂ + i ₃ of the current i _2, and i ₃ is injected as an injection electric i.

FIGS. 8A, 8B and 8C are diagrams for explaining the characteristics of the variable output wavelength bistable elements 910 to 915 in FIG.

FIG. 8A is a diagram showing the relationship between the injection current i and the output light amount P _out when the incident light amount P _in = 0. That is, when the injection current i is increased from 0, i
= I suddenly emitted light amount P _out is increased by _t, the emission light amount P in the case of the injection current i reduced from i> i _t conversely
hysteresis loop, such as _out rapidly decreases with i = i _c - indicates flop, i = i amount of emitted light in _b P _out = P
_It has two stable points, a set state B of ₁ and a reset state A of outgoing light quantity P _out = 0. 8 (b) is a diagram showing the injected current i = i _b the incident light amount P _in the case of the relationship of the emitted light amount P _{ou t} in FIG. 8 (a). That is, when the incident light amount P _in is increased from 0 in the reset state A where the emitted light amount P _out = 0, the emitted light amount P
_out is P _in = increase sharply in P _tb, since the amount of incident light P _in = amount of emitted light in the case of reduced from P _tb to 0 P _out emitted without emitting the little decrease amount P
moves to the set state B of _out = P _l. The reset state A and the set state B in FIG. 8B are respectively shown in FIG.
Represent the same points as in the reset state A and the set state B. Thus i = i _b output wavelength variable was the first reset state A bistable element 910-915 is the amount of incident light P
_In > P _tb , P _out
= _Pl , and can be maintained in the set state B even after the incident light is lost. FIG.
(C) is a diagram showing the relationship between the injection current i = i _O <incident light amount when the i _c P _in the amount of emitted light P _out in FIG. 8 (a). In this case the incident light amount P _in = emission light intensity P _out = 0 At 0, with P _in = P _{t O} is the case of increasing the amount of incident light P _in 0, the emission light intensity P _out increases sharply P _{o ut} = become a P _l, then the amount of incident light P _in
= Become P _{d O} to the exit to decrease amount P _{ou t} = 0. Therefore, at the injection current i = _ib , the output light amount P _out =
Output wavelength tunable bistable element 91 in set state B of P _l
0 to 915 indicate the injection current i if the incident light amount P _in = 0.
Is reduced to i _O , the output light amount P _out = 0
Can be reset. Therefore, if the output wavelength variable bistable element having a hysteresis loop in the injection current versus emission light characteristic is reset in advance with the injection current i = i _O , and then the injection current i = _ib is set, the output wavelength variable The bistable element can store either a binary value, which changes to a set state or is kept in a reset state, depending on the presence or absence of incident light.

Furthermore wavelength of the light emitted from the output wavelength tunable bistable element is injected by the current i constant changing the amount of current distributed to the current i ₂ and i ₃ in FIG. 7, the injected current i and the current i ₂ By increasing the ratio i ₂ / i, the wavelength can be shifted to the shorter wavelength side, and by decreasing the ratio i ₂ / i, the wavelength can be shifted to the longer wavelength side. For details of the variable output wavelength bistable element, refer to the document "Electronics Letters" (ELECTRONIC).
SLETTERS) September 24, 1987, Volume 23, Volume 20
No. pages 1088 to 1089.

FIG. 9 is a time chart for explaining the operation of FIG. Again described case of outputting the third time slot T ₃ wavelengths lambda ₂ of the optical signal of the first time slot T ₁ of the signal output highway 16 of wavelength lambda ₁ of the optical signal on the input highway 1 as an example. The wavelength selection elements 3 and 4 in FIG. 1 are input highways 1 of wavelengths λ ₁ and λ _2.
Since the optical signals of wavelengths λ ₁ and λ ₂ are selected from the signals,
Each of the write optical switches 900 and 901 has a wavelength λ ₁
Input highway 1 signal 1200 and the input highway 1 signal 1201 of wavelength λ ₂ are input. The output wavelength tunable bistable elements 910, 911, and 912 each have an injection current 120
At timings indicated by 2, 1203 and 1204, the amount of injected current is periodically reduced and reset. Then, the write optical switch 900 outputs the output of the wavelength selection element 3 to the output variable bistable element 91 in the order of the first time slot T ₁ , the second time slot T ₂ , and the third time slot T _3.
0, 911.912, the output wavelength tunable bistable elements 910, 911, 912 respectively
One of two values, that is, whether the state changes to the set state or is maintained in the reset state depending on the presence or absence of 5, 1206, and 1207, can be stored. Accordingly, output signals 1208, 1209, and 1210 are output from the output wavelength variable bistable elements 910, 911, and 912, respectively. Here, it is assumed that the output wavelength variable bistable element 910 converts the wavelength of the input signal from λ ₁ to λ ₂ and outputs it. Therefore, the read optical switch 920 switches the output wavelength variable bistable element 91 at the timing of the third time slot T _3.
By reading the output signal 1208 of 0, the light of the first time slot T ₁ of the wavelength λ ₁ of the input highway 1 is output as shown in the output highway 165 signal 1212 of the wavelength λ ₂ among the output highway 16 signals 1211 and 1212. signals, and it is as possible out output to the third time slot T ₃ wavelengths lambda ₂ of the optical signal output highway 16.

FIG. 10 is a diagram showing a specific example of the read optical switches 920 and 912 shown in FIG. According to FIG. 10, the input terminals 1, 2, 3 are respectively the output wavelength variable bistable elements 910, 911, 912 or 913, 91 of FIG.
4,915. The output terminal 4 is connected to the optical coupler 15 of FIG. Optical gate switch 1300,
When the control signal is applied, the optical signals 1301 and 1302 receive the optical signals incident from the input terminals 1, 2, and 3, respectively.
Emitted to 10. Therefore, for example, when the optical signal having the wavelength λ ₁ is input from the input terminal 1 in the first time slot of the time-division multiplexed signal, the control signal is applied to the optical gate switch 1300. For example, in the first time slot, an optical signal having the wavelength λ ₁ is emitted to the output terminal 4. Further, when the optical signals of wavelengths λ ₁ and λ ₂ are input from the input terminal 1 and the input terminal 2 in the first time slot of the time division multiplex signal, for example, the read optical switch of FIG.
If a control signal is applied to both 0 and 1301, optical signals of wavelengths λ ₁ and λ ₂ can be simultaneously output to the output terminal 4 in the first time slot.

[0023] As described above, by using the embodiment of the present invention shown in FIG. 1, the optical signals of any time slot of any wavelength that is input, to any time slot of any wavelength It can be moved. Also in this case, since the configuration is one-stage, the number of optical components can be reduced as compared with the conventional case.

Further, although using a fixed wavelength selection element for selecting each wavelength lambda _1, lambda ₂ of the optical signal wavelength selecting elements 3 and 4 in order to facilitate describing the present invention in FIG. 1, the wavelength lambda ₁ ,
It can be converted into wavelengths long wavelengths of the optical signal selected in each time slot with a variable wavelength selecting element that can be selected by switching either one of the wavelengths for each time slot from lambda ₂ of the multiplex signal, the fixed wavelength The same effect as when the selection element is used can be obtained.

[0025]

As described above, according to the wavelength / time division switch of the present invention, an optical signal of an arbitrary wavelength and an arbitrary time slot can be connected to an arbitrary outgoing line. Thus, the number of optical components can be reduced, and hardware can be reduced.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional optical exchange;

FIG. 3 is a time chart for explaining the operation of FIG. 2;

FIG. 4 is a diagram showing a specific example of a means T ₁₁ for performing time-division switching for each wavelength in FIG. 2;

FIG. 5 is a diagram showing a specific example of means λ12 for performing wavelength division switching for each time slot in FIG. 2;

6 is a diagram showing a specific example of the wavelength conversion element 124 in FIG.

FIG. 7 is a view for explaining one configuration of a variable output wavelength bistable element of FIG. 1;

FIG. 8 is a diagram for explaining characteristics of the variable output wavelength bistable element of FIG. 1;

FIG. 9 is a time chart for explaining the operation of FIG. 1;

FIG. 10 is a diagram showing a specific example of the readout optical switch of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input optical highway 2 Optical splitter 3, 4 Wavelength selection element 5, 6 Tunable wavelength conversion circuit 7, 8 Optical switch 9, 10, 11, 15 Optical combiner 12, 13, 14 Fiber delay line 16 Output optical highway

Claims (2)

(57) [Claims] 1. A wavelength division multiplexed and time division multiplexed optical signal in which a plurality of time division multiplexed optical signals having a plurality of time slots and having different wavelengths are wavelength division multiplexed are input from an input optical highway, and An optical splitter for splitting the wavelength division multiplexed and time division multiplexed optical signal from the optical highway into a plurality of wavelength division multiplexed and time division multiplexed optical signals, and a plurality of wavelength division multiplexing from the optical splitter; A plurality of wavelength selection elements for selecting an optical signal of a specific wavelength from the time-division multiplexed optical signal; and an optical signal having a plurality of output terminals, the optical signals from the plurality of wavelength selection elements being respectively input and for each of the time slots. A plurality of write optical switches that emit light to an arbitrary one of the plurality of output terminals; and a light source that is connected to a plurality of output terminals of the plurality of write optical switches and emits light when incident light is input. And a plurality of output wavelength variable optical storage elements capable of continuously outputting the outgoing light even if the incident light disappears and capable of changing the wavelength of the outgoing light by a control signal. And a read-out matrix optical switch for emitting each of the light emitted from the plurality of output wavelength variable optical storage elements to an output optical highway for each of the time slots. 2. A read matrix optical switch comprising: a plurality of read optical switches for emitting respective optical signals input to a plurality of input terminals to an output terminal for each of the time slots; wavelength-time division optical switching system of claim 1, wherein the configurations of <br/> and a light converging device and outputting the merged optical signal to the output optical highway.