JPH10200540A - Light switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light switch in which respective control of an output wavelength is not required and collision of optical cells is avoided without using plural variable wavelength converters and frequency multiplex buffers. SOLUTION: In an optical switch provided with a variable wavelength light source 1 having plural outputs, plural buffers 21, plural optical modulators 22, a wavelength router 3 and a control circuit 5, connection of each input port and each output port of the wavelength router 3 is decided according to rules for each time slot, and connection of the wavelength router 3 is cyclically switched by switching cyclically a wavelength of the variable wavelength light source 1 for each time slot.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switch technology for switching an optical signal while maintaining light. Further, the present invention relates to an optical switch technology for ATM.

[0002]

2. Description of the Related Art Research and development of large-capacity ATM switching are being actively pursued for realizing a broadband ISDN network. The upper limit of the exchange capacity is mainly determined by the speed limit of the electronic device,
In order to extend this upper limit, optical ATM exchange utilizing characteristics of light has been studied. In particular, if the wavelength of light is used, advantages specific to light can be utilized, and it is possible to overcome the limitations of electronic technology. For that reason, optical switching using wavelength has been studied.

In the present specification, “Optical cell” is an ATM (Asynchronous Transfer Mod)
e) It is defined as an optical signal modulated in the cell of the system. 2. “Time slot” is defined as a cell switching cycle. 3. A “wavelength router” is defined as a device in which output ports are fixedly determined on a one-to-one basis depending on which input port receives light of which wavelength, and a control signal for routing is not externally input.

A conventional configuration example of optical switching using wavelengths will be described with reference to FIG. Optical switch 2 of conventional optical switching technology
00 denotes a plurality of variable wavelength light sources 7, a wavelength router 3, a plurality of frequency multiplexing buffers 8, a plurality of optical receivers 4,
It comprises a variable wavelength light source 7 and a control circuit 5 for controlling the frequency multiplexing type buffer 8. Each frequency multiplexing buffer 8
Comprises a time selector 81 and a wavelength selector 82, respectively. Each variable wavelength light source 7 outputs a wavelength according to a signal from the control circuit 5. The wavelength router 3 sorts the optical cells sent from each variable wavelength light source 7 and sends them to the respective frequency multiplexing type buffers 8. The control circuit 5 sends signals to the variable wavelength light source 7, the time selector 81 and the wavelength selector 82. The time selector 81 of the frequency multiplexing type buffer 8 performs time separation of the optical cells according to the signal from the control circuit 5. The wavelength selector 82 of the frequency multiplexing buffer 8 separates the wavelength of the optical cell according to the signal from the control circuit 5. The optical receiver 4 converts the optical cells sent from the frequency multiplexing type buffer 8 into electric signals and outputs the electric signals.

[0005]

[Table 1]

Hereinafter, the distribution process of the optical cells of the wavelength router 3 will be described with reference to Table 1. Table 1 shows the operation of the wavelength router 3, that is, to which output port O the wavelength router 3 sends an optical cell according to the wavelength of the input optical cell. The wavelength router 3 has input ports I _{1 to} I ₄
And output ports O _{1 to} O ₄ . As shown in Table 1, the wavelength router 3 is an optical device whose destination is switched according to the wavelengths f _{1 to} f ₄ of the input light. For example, the same wavelength f is assigned to a plurality of input ports I ₁ and I ₂ of the wavelength router 3 having the input / output correspondence as shown in Table 1.
_{When one} light is input, the lights are switched to a plurality of output ports O ₁ and O ₄ without overlapping each other, that is, without being multiplexed. Therefore, in order to stabilize the output of the wavelength router 3,
It is necessary to stabilize the wavelength within the cell time.

The switching of the optical cell is performed by converting the wavelength of the optical cell by each variable wavelength light source 7. In this optical switch, since each variable wavelength light source 7 converts the wavelength to an arbitrary wavelength, a plurality of optical cells may be multiplexed and arrive at one output port at the same time. In this case, time separation is performed in the time selector 81, wavelength separation is performed in the wavelength selector 82, and one optical cell is output from the frequency multiplexing type buffer 8.
Output one at a time slot.

The advantage of this method is that an output buffer type optical ATM switch capable of high throughput can be constructed. However, the problems of this method include: In this optical ATM switch, a plurality of optical cells may be multiplexed and arrive at one output port at the same time, and a frequency multiplexing buffer 8 for demultiplexing is required. The information rate is 10 Gb / s and the information amount of one cell is 53 b
If one byte (8 bytes), one cell time is (53 × 8 bits) ÷ (10 Gbit / s) = 4
2.4 ns. Therefore, in order to separate the time of the optical cell, the time of the optical cell must be shifted by 42.4 ns. Therefore, this optical switch requires an expensive optical memory which is still under research. In addition, a variable wavelength filter is required for wavelength separation.

[0009] 2. The main parameters that determine the output wavelength of the tunable light source 7 are the current value injected into the tunable light source 7 and the temperature of the tunable light source 7. Switches. In order to control the output wavelengths of the plurality of variable wavelength light sources 7 at random, it is necessary to adjust these parameters which change in a complicated manner, which is not easy to realize.

[0010] 3. Since the multiplicity of the optical cell output from the wavelength router 3 changes, the input light intensity to the frequency multiplexing buffer 14 changes. For example, when the number of optical cells input to one time slot in the frequency multiplexing buffer 8 changes from 1 to 4, the light intensity changes four times between the minimum value and the maximum value, and the frequency multiplexing type having a large dynamic range by that amount. The buffer 8 is required and the design becomes difficult.

For the above reasons, a plurality of variable wavelength light sources 7
There is no need to randomize the output wavelengths of the optical switches, and there is a demand for an optical switching system using wavelengths in which optical cells are not multiplexed inside the switch. As a similar example of this embodiment, there is one reported in IEICE Autumn Conference B-383 in 1993.

[0012]

SUMMARY OF THE INVENTION As described above, in the prior art: A plurality of optical cells are multiplexed at the output port of the wavelength router 3. Therefore, a frequency multiplexing type buffer 8 for demultiplexing is required, and hardware is increased. 2. Since the output wavelengths of the plurality of variable wavelength light sources 7 are each controlled at random, implementation is not easy. Since the degree of multiplexing of the output optical cells of the wavelength router 3 changes, the intensity of the input light to the frequency multiplexing buffer 8 changes arbitrarily, which causes a problem that the design of the frequency multiplexing buffer 8 becomes difficult. .

An object of the present invention is to solve the problem of increasing the hardware of the optical switch. Another object of the present invention is to solve the problem that a plurality of complicated control circuits for the variable wavelength light source 7 are required. Further, another object of the present invention is to solve the problem of a large output light intensity fluctuation of the wavelength router 3.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to provide a variable wavelength light source having a plurality of optical outputs, a control circuit, a plurality of buffers for buffering input cells, and a plurality of optical modulators for modulating light with the input cells. And a wavelength router having a plurality of input / output ports.

The variable-wavelength light source having a plurality of outputs transmits continuous light having the same wavelength to each optical modulator from a plurality of outputs in one cell time, and simultaneously converts the wavelengths of the plurality of continuous lights to another wavelength for each time slot. Switch. The control circuit outputs a signal to each buffer at the timing when the wavelength reaches a wavelength at which the optical cell is transmitted to a desired output port, in synchronization with the variable wavelength light source. Each buffer outputs a cell according to a signal from the control circuit. Each optical modulator modulates continuous light from a plurality of outputs of a variable wavelength light source according to input information according to cell information from a buffer. That is, each optical modulator modulates continuous light input from a multiple-output variable wavelength light source into an optical cell in the time slot in which a signal from the control circuit is transmitted, and transmits the modulated light to each input port of the wavelength router. . The wavelength router outputs an optical cell as an output signal from each output port that is regularly determined by the input port and wavelength of the optical cell input to each input port.

By the above operation, the wavelengths of the plurality of optical cells are switched to another wavelength at the same time every one cell time, and the connection between each input port and each output port of the wavelength router is cyclically switched.

1. In the present invention, an optical signal of one wavelength is input to each input port of the wavelength router, so that those optical signals do not go to the same output port but are sent to each output port on a one-to-one basis.
It is distributed to. Therefore, the frequency multiplexing type buffer 8 for demultiplexing becomes unnecessary.

2. Since only one variable wavelength light source is prepared and the output wavelength is controlled, only one control circuit for the variable wavelength light source is required.

3. Since the multiplicity of the optical cell output from the wavelength router can always be 1, the level fluctuation of the light intensity is smaller than in the conventional case. Therefore, the design of the optical receiver becomes easy.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an embodiment of an optical switch according to the present invention will be described with reference to FIG. In the figure, a thick line indicates a signal transmitted electrically, and a thick broken line indicates light and a signal transmitted as light. The optical switch 100 according to the present invention includes a variable wavelength light source 1 having a plurality of optical outputs.
When a plurality of light modulation means 2, an input port I ₁ ~I ₄ and the output port O ₁ ~ O ₄ wavelength router 3 having the optical receiver demodulates the optical modulated light cell CL to the output cell Cs 4 and a control circuit 5.

The tunable wavelength light source 1 having a plurality of optical outputs includes:
An output variable wavelength light source 11 and an optical coupler (branch device) 12 that splits the output of the single output variable wavelength light source into a plurality of optical outputs.
have. Each optical modulating means 2 includes a buffer 21 for buffering the input cell Ci, and an optical modulator 22 for modulating the light of the wavelength f input from the variable wavelength light source 1 with the signal of the input cell Ci and outputting it as an optical cell CL. have. In this embodiment, the number of input / output ports of the wavelength router 3 is set to four, but these may be any values.

An example of the configuration of the one-output variable wavelength light source 11 will be described with reference to FIG. The one-output variable wavelength light source 11 includes a plurality of fixed wavelength light sources 111 made of, for example, a semiconductor laser.
, An optical gate 112 connected to the output of each fixed wavelength light source 111, and an optical coupler 113 to which the output of each optical gate is input and output as one output. The fixed wavelength light source 111-1～111-4 outputs continuous light, respectively different wavelengths (f ₁ ~f _4). Optical gate 112
Can be realized using an electric absorption type optical gate, a semiconductor optical amplification type optical gate, and an interference type optical gate. The optical gate 112 is turned on and off by a control signal from the control circuit 5.
It is flip-flopped and transmits light when in the ON state and does not transmit light when in the OFF state. The variable wavelength light source 11 outputs light of an arbitrary wavelength f depending on which optical gate 112 is turned on.

The operation of the variable wavelength light source 11 will be described with reference to FIG. In FIG. 3, the horizontal axis is time (time slot).
T and the vertical axis represents the output wavelength f. The one-output tunable wavelength light source 11 cyclically switches the output wavelength f for each time slot T and outputs. When a long time is required for wavelength switching, a guard time t can be provided between cells. The time slot T is composed of a cell time Tc and a guard time t, and it is necessary that the wavelength is stable within the cell time Tc. In this example, the fixed wavelength light source 11
And ON the optical gate 112-1 outputs a light having a wavelength f ₁ in the time slot T ₁ of the from 1-1, the fixed wavelength light source 111-
Optical gates 1 light of wavelength f ₂ from 2 in the time slot T ₂
Turn on 12-2 and output. After this, likewise the light of the wavelength f ₃ in the time slot T _3, and switching and outputting light having a wavelength f ₄ in the time slot T _4, and outputs again the wavelength f ₁ light in the time slot T _5, The wavelength is switched cyclically. This wavelength switching is performed during the guard time t.

The control circuit 5 detects the destination of the input cell from the information on the destination included in the input cell Ci, and sends a signal to each buffer 21 at the timing of the wavelength at which the optical cell CL is sent to the corresponding output port. And each buffer 21 also outputs the signal of the input cell Ci to each optical modulator 22 at that timing. Each optical modulator 22 includes an optical coupler 1
2 is modulated according to the signal of the input cell Ci and output as the optical cell CL.

The operation of the wavelength router 3, that is, the output port to which the optical cell CL input to each input port I is transmitted by the wavelength router 3 according to its wavelength will be described with reference to Table 2 and FIG.

[0026]

[Table 2]

As shown in Table 2, the wavelength router of the present invention is regulated so that signals input to a plurality of input ports are not output from the same output port in the same time slot.

As described in detail below, the wavelength router 3 outputs the optical cell CL output from each optical modulator 22 from each input port of the optical cell CL and each output port that is regularly determined by the wavelength. In this example, the wavelength router 3
The wavelength f _{1 at the} time slot T ₁ (T ₅ , T 9,...)
The optical cell CL, the input ports and output ports O ₁ light cell CL input from I _1, an optical cell CL inputted from the input port I ₂ to the output port O _4, is inputted from the input port I ₃ light cell CL to the output ports O _3, an input port I
And outputs the optical cell CL inputted from ₄ to output port O _2. Next, the wavelength router 3 sets the time slot T _{2
(T6, T 1 0, ...} ) the wavelength of the optical cell CL f _2, the optical cell CL inputted from the input port I ₁ to the output port O _2, light cells inputted from the input port I ₂ CL when the to the output port O ₁ and the optical cell CL inputted from the input port I ₃ to the output port O _4, and outputs the optical cell CL inputted from the input port I ₄ to the output ports O _3.

Further, for the optical cell CL having the wavelength f _{3 in} the time slot T ₃ (T 7, T ₁₁ ,...), The wavelength router 3 converts the optical cell CL input from the input port I ₁ to the output port O. ₃ , the optical cell CL input from the input port I ₂
To the output port O ₂ and the optical cell CL inputted from the input port I ₃ to the output port O _1, and outputs the optical cell CL inputted from the input port I ₄ to the output port O _4. Next, the wavelength router 3 sets the time slot T ₄ (T8, T
₁ 2, ...) output port O on the optical cell CL of wavelength f _4, a light cell CL inputted from the input port I ₁ when the
To _4, a light cell CL inputted from the input port I ₂ to the output port O _3, the optical cell CL inputted from the input port I ₃ to the output port O _2, light cells inputted from the input port I ₄ CL output the to the output port O _1.

[0030] Since the time slot T in ₅ again wavelengths _{f 1, (I 1 -O 1} ) (I 2 -O 4) (I 3 -O 3) (I 4 -
O ₂ ). Similarly, the connection between each input port and each output port is cyclically changed for each time slot.

As described above, in the present embodiment, in the same time slot, the input port I _{1 of the} wavelength router 3 is used.
~I ₄ same optical cell CL of wavelengths input to, so is output to different output ports O ₁ ~ O _4, respectively, light cells CL to be input to the input port I ₁ ~I ₄ simultaneously without being multiplexed Each is output to a different output port. The optical cells CL output from the wavelength router 3 are input to the optical receiver 4, respectively, converted into output cells Cs for electric signals, and output.

FIG. 5 shows an example of the timing of an input cell Ci input to the buffer 21 and its destination (output port). In the time slot T _1, buffer 21-1～21-
4 destination cell C ₁ -C ₄ in O ₁ is input to. In the time slot T _2, the cell C ₅ destination of O ₁ to the buffer 21-1
But the destination cell C ₆ of O ₁ is input to the buffer 21-3. In the time slot T _3, cell C ₇ destinations O ₁ in the buffer 21-1, the cell C ₈ destinations of O ₄ buffer 21-4 is input in the time slot T _4, the buffer 21
The cell C ₉ whose destination is O ₁ is input to ₁ . Here, an example in which the cell C is concentrated to the output port O _1, illustrating the ability to avoid a collision cell by a buffer 21.
During the time slots T _{1 to} T ₅ , the input port I
Is to ₁ it is assumed that only a cell of output port O ₁ bound not enter.

FIG. 6 shows the relationship between the connection between the input port I and the output port O for each time slot T (wavelength f), the cell Ci input to the buffer 21, and the cell read from the buffer 21 at this timing. The relationship of Ci will be described. In the figure, one square represents a buffer for storing one cell, and a square surrounded by a thick frame represents an output port O connected to the input port I. In this embodiment, each buffer 21 is configured to be able to store up to 16 cells, and each buffer 21 is configured to store four cells for every four output ports. However, the number of cells stored in the buffer can be any value.

[0034] In time slot T _1, each buffer 21
Output port O ₁ bound cell C ₁ -C ₄ the inputs to 1～21-4. In the time slot T _1, since the output wavelength f ₁ of the variable wavelength light source 1, the input cell C ₁ is taken from the output port O ₁ area of the buffer 21-1, the optical modulator 22-1
In is output to be optically modulated to the output port O ₁ as an optical cell CL. On the other hand, since the input cells I are not connected to the output port O ₁ , the input cells C ₂ , C ₃ , and C ₄ are stored in the output port O ₁ areas of the buffers 21-2, 21-3, and 21-4, respectively. Is stored.

Time slot T_TwoNow, the variable wavelength light source 1
Output wavelength of f_TwoTherefore, the output port of the buffer 21-2 is
O₁Cell C stored in area_TwoIs taken out and output
Port O₁Output to On the other hand, input cell C_Five, C
₆Are output ports of buffers 21-1 and 21-3, respectively.
O₁Stored in the area. Time slot T_ThreeSo, variable
The output wavelength of the wavelength light source 1 is f_ThreeSo, input cell C ₇Is
Output port O of F21-1₁Area, but
Output port O of buffer 21-4_FourInput entered in the area
Cell C₈Output port O_FourTowards
Is output. At the same time, the output port O of the buffer 21-3
₁Cell C stored in area_ThreeIs taken out and the output port
O₁Output to. Time slot T_FourOK
The output wavelength of the variable wavelength light source 1 is f_FourSo, input cell C₉Is
Output port O of buffer 21-1₁Stored in the
Output port O of F21-4₁Cell C stored in area_Four
Is taken out and the output port O₁Output to. same
In time slot 5, the input cell C₉Is buffer 2
1-1 output port O₁Variable wavelength light source input to the area
The output wavelength of 1 is f₁Therefore, the output port of the buffer 21-1 is
O₁Cell C stored in area_FiveIs taken out
The output port is optically modulated by the modulator 22-1 and output as the optical cell CL.
O₁Output to.

With the above operation, the buffer stores cells for each output port, and stores the optical cell C in the desired output port.
The cell can be output at the timing when L becomes the wavelength to be transmitted.

As described above, in this embodiment, the optical cell CL is switched by switching the wavelength f for each time slot T. Since only one wavelength is used in each time slot, it can be implemented only by branching and using the output of one variable wavelength light source 1. Further, since the output wavelength is simply switched cyclically, control of the variable wavelength light source 1 is also easy.

As described above, even when the cells of each input port have the same destination and the cells of a certain input port have the same destination continuously, the optical ATM switch according to the present invention can process without problems. Can be.

In this embodiment, the connection between each input port and each output port can be switched randomly by switching the output wavelength of the variable wavelength light source 1 at random according to need, instead of a fixed rule. It is clear. Although the optical ATM switch has been described in the present embodiment, the optical switch according to the present invention is not limited to the optical ATM switch.
Optical STM (Synchronous Transfer)
Mode) and connection switching of a parallel optical computer.

Hereinafter, the output wavelengths f ₁ .
f ₂ . f ₃ . If you think a cyclic combination of f _4, 1. By repeating f ₁ , f ₂ , f ₃ , f ₄ , f ₁ , f ₂ , f ₃ , f ₄ ..., the control of the variable wavelength light source 1 becomes easy. 2. f ₁ , f ₁ , f ₂ , f ₂ , f ₃ , f ₃ , f ₄ , f ₄ , f ₁ ,
By repeating the same wavelength a plurality of times, f ₁ , f ₂ , f ₂ , f ₃ , f ₃ , f ₄ , f ₄ , etc., the number of times of connection switching can be reduced, and the control of the variable wavelength light source 1 is further improved. It will be easier. 3. f ₁ , f ₁ , f ₂ , f ₃ , f ₄ , f ₁ , f ₁ , f ₂ , f ₃ ,
Repeating f ₄ ... is effective when the connection is biased to a certain wavelength. 4. _{f 1, f 2, f 1} , f 3, f 1, f 4, f 1, f 2, f 1,
f ₃ , f ₁ , f ₄ ... or f ₁ , f ₁ , f ₂ , f ₁ , f ₁ ,
f ₃ , f ₁ , f ₁ , f ₄ , f ₁ , f ₁ , f ₂ , f ₁ , f ₁ , f ₃ ,
f ₁ , f ₁ , f ₄ ..., f ₁ is a fundamental wavelength, and f _1
2, f _3, a method of inserting a f ₄ is.

As described above, by cyclically switching the wavelength, the value of the current injected into the fixed wavelength light source 111 constituting the variable wavelength light source 1 is averaged, so that the temperature of the fixed wavelength light source 111 is stabilized. In addition, the control of the variable wavelength light source 1 becomes easy.

[0042]

The present invention has the following effects. 1. Since a frequency multiplexing type buffer is not required on the output port side of the wavelength router 3, a reduction in the amount of hardware of the optical switch can be expected. 2. In one time slot, light of the same wavelength is modulated at each input, so that the output of one variable wavelength light source 11 may be branched, and the wavelength of the variable wavelength light Control becomes easy. 3. Since the number of multiplexed optical cells CL from the wavelength router does not change, the design of the optical switch becomes easy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the concept of the configuration of an embodiment of an optical switch according to the present invention.

FIG. 2 is a block diagram showing a configuration of a one-output tunable wavelength light source 11;

FIG. 3 is a time chart showing an output state of a variable wavelength light source 1 having a plurality of optical outputs.

FIG. 4 is a diagram illustrating an operation mode of the wavelength router according to the present invention.

FIG. 5 is a view for explaining the state of cells input to a buffer 21;

FIG. 6 is a diagram illustrating an operation mode of a buffer 21.

FIG. 7 is a block diagram showing the concept of the configuration of an optical switch according to the related art.

[Explanation of symbols]

Reference Signs List 1 variable wavelength light source having plural optical outputs 11 1 output variable wavelength light source 111 fixed wavelength light source 112 optical gate 113 optical coupler 12 optical coupler (branch device) 2 optical modulator 21 buffer 22 optical modulator 3 wavelength router 4 optical receiver Reference Signs List 5 control circuit 7 variable wavelength light source 8 frequency multiplexing buffer 81 time selector 82 wavelength selector I _{1 to} I ₄ input port O _{1 to} O ₄ output port

Claims (4)

[Claims] 1. An optical switch comprising a plurality of output variable wavelength light sources, a plurality of optical modulators, and a wavelength router having a plurality of input / output ports, wherein the plurality of output variable wavelength light sources are used for one cell time. A variable wavelength light source that performs an operation of simultaneously transmitting continuous light of one wavelength from a plurality of outputs to each of the optical modulators and switching the wavelength of the plurality of continuous lights to any one wavelength at a time slot; Each of the optical modulators is an optical modulator that modulates continuous light input from the multiple-output tunable wavelength light source according to input information and sends the modulated light as an optical signal to each input port of the wavelength router. A wavelength router that outputs an optical signal from each output port that is regularly determined by the input port and wavelength of the optical signal input to the port. The input information is obtained by multiplexing the optical signal from the output port of the wavelength router. Optical switch, characterized in that it is outputted in accordance without wavelength and rules that. 2. An optical switch comprising a multiple-output variable wavelength light source, a plurality of optical modulators, and a wavelength router having a plurality of input / output ports, wherein the multiple-output variable wavelength light source is used in one cell time. Continuous light having the same wavelength is sent to each of the optical modulators from a plurality of outputs,
A variable wavelength light source that cyclically switches the wavelengths of a plurality of continuous lights to another wavelength for each time slot; and wherein each of the optical modulators is a continuous light input from the plurality of output variable wavelength light sources. Is an optical modulator that modulates according to the input information and sends it as an optical signal to each input port of the wavelength router, wherein the wavelength router is configured to regularly output the input signal and the wavelength of the optical signal input to each input port. An optical switch for outputting an optical signal from a port, wherein input information is cyclically output from each output port of the wavelength router without being wavelength-multiplexed. 3. An optical switch comprising a variable output light source having a plurality of outputs, a control circuit, a plurality of buffers, a plurality of optical modulators, and a wavelength router having a plurality of input / output ports. The variable wavelength light source sends continuous light having the same wavelength in one cell time from a plurality of outputs to each of the optical modulators,
A variable wavelength light source that performs an operation of cyclically and simultaneously switching the wavelengths of a plurality of continuous lights to another wavelength for each time slot, wherein each buffer buffers input information and operates in accordance with a signal from the control circuit. A buffer that outputs a signal to each of the optical modulators in a time slot of a wavelength at which an optical cell is sent to a desired output port, wherein each of the optical modulators is a time slot in which a signal is sent from the control circuit; An optical modulator that modulates the input continuous light according to a signal from the buffer and sends it as an optical cell to each input port of the wavelength router, wherein the wavelength router has an input port and wavelength of the optical cell input to each input port. A wavelength router that outputs an optical cell from each output port that is regularly determined by the input information, wherein the input information is multiplexed from each input port according to a wavelength. An optical switch characterized in that a signal is output cyclically from each output port of the wavelength router without being output. 4. The wavelength router according to claim 1, wherein in the same time slot, input information input to a plurality of input ports is regulated so as not to be output from the same output port. Light switch.