JPH0897830A - Optical time division exchange system - Google Patents

Abstract

PURPOSE: To eliminate the need of control and synchronization, to save electric power and to accelerate a speed by processing optical input cells in the coupler, periodic type filters, delay elements, coupler and BPFs of passive elements after wavelength converting them in an input I/F module. CONSTITUTION: A (k)×(m) coupler 20 converts outputs for which (k) pieces of the optical input cells are wavelength converted by the input I/F module 10 to (m) pieces of the outputs and outputs them to (m) pieces of the periodic filters 21. The filters 21 pass through only the cells of a wavelength in a fixed period and (m-1) pieces of fiber delay lines 22 give the delay amount of (m-1)T (T is the time slot of the optical cells) to them. For the outputs for which (m) pieces of inputs from one filter 21 and (m-1) pieces of delay lines 22 are converted to (k) pieces by an (m)×(k) coupler 23, (k) pieces of the BPFs(band-pass filters) pass through only the cells of the wavelength of a prescribed band. Thus, since self routing and buffering elements are provided and everything except the module 10 is the passive element, the need of the control and the synchronization is eliminated and a processing is performed at a high speed with low power consumption.

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 switching system having self-routing and buffering elements, and more particularly to an optical time division switching system for synchronous (STM) and asynchronous (ATM) optical time division. Regarding

[0002]

2. Description of the Related Art In multimedia, the amount of information dramatically increases and cannot be processed by the current communication network. For that purpose, a wideband ISDN is being constructed as a next-generation communication network. On the other hand, in the wide band communication network, information exchange is an important element, and a large capacity exchange system capable of processing a huge amount of information is desired. Optical switching is expected as one of them.

FIG. 17 shows an example of the configuration of a conventional system, and particularly, a configuration for ATM (asynchronous transfer mode) exchange. Optical cells arrive from k input lines and enter the input interface module (IIM) 1. The input interface module 1 decodes the VCI (virtual channel identifier) of the optical cell and outputs the tag indicating the path information of the internal optical switch in addition to the optical cell.

Each optical cell / tag pair is input to the corresponding 1 × k optical switch 2. The optical switch 2 is
The optical cell is output to either route according to the tag information. The optical cells from each optical switch 2 are input to the buffer 3 in order to avoid collision, and k optical cells are output from the output line from the buffer 3.

The control circuit 4 controls the operations of the input interface module 1 and the buffer 3. Since each optical cell undergoes necessary buffering, it is distributed to the buffer 3 having a delay amount corresponding to the buffering time by the 1 × k optical switch 2 according to the control signal from the control circuit 4.

Further, FIG. 18 shows another example of the configuration of the conventional system, in particular, an example of a synchronous transfer mode (STM) switching system.

In this structure, the spatial light switch 5 of k × k and the time switches 6 and 7 provided on the input side and the output side thereof are provided. Further, the arriving time-division multiplexed optical signal is converted into an electric signal in the input interface module 1 provided for each corresponding incoming line and input to the signal processing unit 45.

The signal processing unit 45 synchronizes with the clock signal from the synchronizing circuit 47 and sends a control signal for exchanging time slots to the drive circuit 46. The main signal is converted back into an optical signal in the input interface module 1 and the time slot positions are exchanged in the time switch 6 in order to prevent collision in the space switch 5 in the next stage.

Next, the space switch 5 switches to a desired outgoing line based on a control signal from the drive circuit 46 for each time switch. The output of the space switch 5 is further switched to a desired time slot position by the time switch 7 in the subsequent stage.

[0010]

The above-mentioned conventional AT is used.
In the M-exchange, switching must be performed for each optical cell, buffering must be performed to avoid collision of optical cells, and it is necessary to control the optical switch 2 and the buffer 3. This control is performed by the control circuit 4, and the control is performed by an electric signal. Therefore, there is a speed limit and a high degree of control is required. Furthermore, as the number of active elements increases, optical components are required to have high reliability.

In the conventional example shown in FIG. 18, all the time switches 6 are controlled by the control signal from the signal processing section 45.
7. It is necessary to operate the space switch 5 in synchronization with each time slot.

However, synchronous control of the entire system becomes more difficult as the signal speed increases.
Further, the conventional configuration example of FIG. 18 has a configuration of time switch-space switch-time switch, and a drive circuit for them is also required, and the hardware scale is large.

In addition, in order to perform non-blocking exchange, another set of this switch structure is required, and the hardware structure becomes larger.

Therefore, the present invention has been made in view of such conventional problems, and provides an optical time division switching system of low power consumption and large capacity for exchanging optical information from an optical fiber as it is. It is intended to be provided.

[0015]

The basic configuration of the optical time division switching system according to the present invention is, in one aspect, to receive k optical input cells and perform wavelength conversion of each optical input cell. The input interface module to be performed, the k × m coupler that receives the output of the input interface module and converts it into m outputs, and the outputs of the k × m coupler, respectively M periodic filters to be passed, and m delay elements that receive respective outputs of the m periodic filters and give a delay amount of (m-1) T (T is a time slot of an optical cell). , An m × k coupler that receives each output of the m delay elements and converts the output into k outputs, and k bands that receive each output of the m × k coupler and allow only cells of wavelengths in a predetermined band to pass. Have a pass filter The features.

[0016] In another aspect, an input interface module for receiving k optical input cells and performing wavelength conversion of each optical input cell, and an output of the input interface module for receiving m optical outputs. Receiving the respective outputs of the k × m coupler and the k × m coupler for passing only cells of wavelengths in a predetermined band and receiving the respective outputs of the m bandpass filters. , (M−1) T (T is a time slot of an optical cell) and m delay elements for giving a delay amount and outputs of the m delay elements, and are converted into k outputs m × It is characterized by having m number of periodic filters which receive the outputs of the k coupler and the m × k coupler and pass only the cells having the wavelength of the constant period.

According to the above aspect, the input interface
The module performs wavelength conversion corresponding to the route of the outgoing line for the optical cells reaching each incoming line. As a result, k × m
Everything after the coupler is processed by light regardless of electric signals.

As a result, the optical cell can be exchanged as it is, and a low power consumption and large capacity optical time division switching system can be realized.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description of the embodiments of the present invention with reference to the drawings, the same or similar parts are designated by the same reference numerals and symbols.

FIG. 1 is a block diagram of a first embodiment of an optical time division switching system of the present invention. In FIG. 1, reference numeral 10 is an input interface module (IIM) that receives k optical input cells and performs wavelength conversion of each input.

Further, 20 is a k × m coupler which receives the output of the input interface module 10 and converts it into m outputs. 21 is this k × m coupler 20
M periodic filters which receive each of the m outputs and pass only the optical cells having a fixed cycle wavelength.

Here, the periodic filter 21 is shown in FIG.
As shown in the transmission characteristic of I of (2), it is a Fabry-Perot type filter having a narrow transmission width, has a predetermined transmission wavelength interval (FSR: free spectrum range), and has a periodic transmission characteristic. Have.

Reference numeral 22 denotes (m-1) delay elements that receive the outputs of these periodic filters 21 and send them for a predetermined time. As an example, 1T, 2T, ...
A fiber delay line that gives a delay amount of (m-1) T is adopted.

Reference numeral 23 denotes the (m-1) delay elements 22.
Is an m × k coupler that receives the output of the above and converts it into k outputs. Reference numeral 24 is a bandpass filter (BPF) having a pass characteristic of k predetermined widths, which receives each output of the m × k coupler 23 and passes only the optical cells having wavelengths of a predetermined band.

Here, referring to FIG. 1B, there is shown the relationship between the periodic transmission characteristic of the periodic filter 21 and the transmission characteristic of the bandpass filter 24 having a predetermined width. FS
For the periodic type filter 21 having a transmission characteristic of a periodic narrow band with an R wavelength interval, a band pass filter (B
Since PF) has a pass characteristic of a predetermined width, wavelengths λ1 to λm, ... λ from the k bandpass filters 24 are sequentially shifted by sequentially shifting the transmission wavelength of the periodic filter 21.
It is possible to selectively output an optical cell having a wavelength of (k−1) m + 1 to λkm.

As described above, the input interface module 10 of the first embodiment performs wavelength conversion corresponding to the route of the outgoing line with respect to the optical cell entering from each incoming line. As a result, after the k × m coupler 20, all the signals can be processed by light without requiring an electric signal.

Therefore, by exchanging the optical information from the optical buffer as it is, it is possible to realize an optical switching system with low power consumption and large capacity.

FIG. 2 is a block diagram of the second embodiment.
In this embodiment, the front and rear positions of the periodic filter 21 and the bandpass filter 24 of the first embodiment are interchanged.

Therefore, the operating characteristic is the same as the first characteristic of FIG.
Since it is the same as the embodiment described above, further description will be omitted.

FIG. 3 is a block diagram of the third embodiment.
This embodiment is similar to the bandpass filter 24 of the first embodiment.
After that, the output interface module 25 for converting all the optical cells of the respective wavelengths into the optical cells of the same wavelength
Is provided.

In the third embodiment, the output interface module 25 provided after the output line of the first embodiment converts all the wavelengths of the optical cells of the output line to the same wavelength. This facilitates the subsequent handling of the optical cell.

FIG. 4 is a block diagram of the fourth embodiment.
In this embodiment, after the periodic filter 21 of the second embodiment, an output interface module 25 for converting all optical cells of respective wavelengths into optical cells of the same wavelength is provided.

Also in the case of the fourth embodiment, the output interface module 30 is provided after the outgoing line of the second embodiment.
Is provided so that all the wavelengths of the optical cells on the outgoing line are converted into the same wavelength, the subsequent optical cells can be easily handled.

FIG. 5 is a block diagram showing the configuration of the fifth embodiment of the present invention. In this embodiment, k × m in FIG.
The coupler 20 is a k × 1 coupler 201 and a 1 × m coupler 203.
And the m × k coupler 23 is separated into m × 1 coupler 231.
And 1 × k coupler 233, and optical amplifiers 202 and 232 for optical amplification are provided between the respective couplers.

As the optical amplifiers 202 and 232, for example, erbume doped fiber amplifiers or the like are used.

With such a structure, the optical cell attenuated during the transmission can be returned to the original optical cell having the optical intensity. In this embodiment, k × 1 coupler 201 and 1 ×
An example is shown in which the optical amplifiers 202 and 232 are provided between the m coupler 203 and between the m × 1 coupler 231 and the 1 × k coupler 233, but a configuration in which at least one of them is provided is possible.

In this embodiment, the case where the optical amplifier is provided in the first embodiment shown in FIG. 1 is shown.
In the second to fourth embodiments shown in FIG.
Can be provided.

According to the fifth embodiment, after the k × 1 coupler 201, only optical signals are used, and no electric signals are present. Therefore, the optical information from the optical fiber can be exchanged as it is. Further, it is possible to compensate the intensity of the optical cell that is attenuated during the transmission and restore it to the original state.

Further, in each of the above-mentioned embodiments, the input interface module 10 is composed of a wavelength conversion section provided for each input line and a signal processing section for controlling the operation of each wavelength conversion section. It is preferable to ensure wavelength conversion of each input. Such a configuration will be described later again in the specific operation description.

FIG. 6 is a diagram showing a specific configuration of the input interface module (IIM) 10 commonly used in the case of configuring the optical ATM switching system in the configuration block diagrams of the above embodiments.

In the figure, the input interface module 10 receives k optical cell inputs and performs wavelength conversion of each input, so that the wavelength conversion unit 40 and each wavelength conversion unit 40 are provided for each incoming line. It is configured to have a signal processing unit 45 for controlling the operation of.

The wavelength converter 40 is an optical / electrical converter (O /
E) 41, wavelength tunable laser diode (LD) 42, modulator 43, and delay circuit 44. The material of the modulator 43 is, for example, LiNbO ₃ (LN).
Etc. are used.

The operation of the above-described first embodiment having the input interface module 10 thus constructed will be described below.

When the optical cell of wavelength λ 0 arrives at the input interface module 10 from each incoming line, the optical / electrical converter 41 is input to the input interface module 10.
Converts the optical signal into an electrical signal. The optical cell converted into an electric signal is input to the signal processing unit 45.

In the signal processing unit 45, the VCI (virtual channel identifier) of the inputted optical cell signal is analyzed, the outgoing line of the optical cell is judged, and further, there is an optical cell simultaneously output to the same outgoing line. Monitor and perform contention control.

When the output line is determined, the signal processing unit 45 drives the wavelength tunable laser diode 42 of each wavelength conversion unit 40 to emit light at a wavelength corresponding to the output line and the buffering time. The light emitted from the wavelength tunable laser diode 42 enters the modulator 43 that follows and is modulated according to the input signal.

Here, the output of the wavelength tunable laser diode 42 is modulated by the modulator 43 by the output of the optical / electrical converter 41, but the signal processing section 45 finishes the analysis after receiving the output of the wavelength tunable laser diode 41. Since it takes time to complete, the delay circuit 4
After being delayed by 4, the signal is input to the modulator 43.

In this way, the wavelength of the optical cell is converted by the input interface module 10 into one specific wavelength based on the relationship between the outgoing line and the delay time and output.
These k outputs enter the subsequent k × m coupler 20 and m
Are branched to outputs. The m outputs respectively enter the corresponding periodic filters 21, and in each filter,
Only the optical cells with a fixed cycle wavelength are transmitted.

Since these periodic filters 21 transmit only the light of the wavelength for each fixed period, they are all set to m different wavelengths within the period. That is, according to the transmission characteristic I of the periodic filter shown in FIG. 1B, only the optical cells of wavelengths (λ1, λm + 1 ... λnm + 1) arranged at a constant period are transmitted.

In the figure, the first stage of the periodic filter [FIG.
In (1), the characteristics of the periodic filter shown in the uppermost stage are shown, but the characteristics of the periodic filters of the other stages are also the same.

Only the optical cells that match the set transmission wavelength of these periodic filters 21 are transmitted, and the following delay element 22, that is, a fiber delay line is used as an example, and is input to this. Only the first stage of the fiber delay line 22 has a delay amount of 0,
The second stage has a delay of 1T, the third stage has a delay of 2T, and the final stage (m
The first fiber delay line) has a delay amount (m-1) T.

Here, T represents a time slot, and 1T
Is delayed by one optical cell, and the number of time slots is gradually increased as it goes to the lower stage.
The delay of the fiber delay line 22 at the final stage has a number of time slots (m-1) and a delay amount (m-1) T.

Then, in these fiber delay lines 22,
Only optical cells with different output lines but equal delay times pass. The output of the m fiber delay lines 22 is m ×
The k coupler 23 branches into k pieces and outputs.

Each of these k outputs enters the bandpass filter 24. The transmission wavelength setting range of these bandpass filters 24 corresponds to one cycle of the periodic filter 21, that is, FSR, as indicated by II in FIG. 1 (2).
Further, the center wavelength of the transmission wavelength setting range of the bandpass filter 24 is set to a different wavelength for each outgoing line.

Therefore, for example, the bandpass filter 24 in the first stage transmits wavelengths of λ1 to λm, and the bandpass filter 24 in the final stage transmits wavelengths of λ (k-1) m + 1 to λkm. I will let you.

In this way, the bandpass filter 24
Only the optical cells in the set wavelength range of
It is output to each output line. Therefore, the k × m coupler 20
After that, all the signals are optical signals, and no electric signals are present. Therefore, optical information from the optical fiber can be exchanged as it is, and an optical switching system with low power consumption and large capacity can be provided.

The operation of the second embodiment of FIG. 2 using the input interface module 10 of FIG. 6 will be described below.

As in the first embodiment shown in FIG. 1, the input interface module 10 determines the wavelength of the optical cell entering from the incoming line, one wavelength from the relationship between the outgoing line and the delay time, and Do the conversion. Input interface
The optical cell output from the module 10 is branched into m cells by the k × m coupler 20.

Each output of the k × m coupler 20 is passed through the band pass filter 24, and only the optical cell of a predetermined frequency band is transmitted to the fiber delay line 22.

Optical cells having different outgoing lines can simultaneously pass through the fiber delay line 22. After that, the optical cell transmitted through the fiber delay line 22 is k by the m × k coupler 23.
Branched into pieces. In the branched optical cell, only the component of a predetermined wavelength is transmitted by the subsequent periodic filter 21 and output from the output line.

Also in this second embodiment, after the k × m coupler 20, only optical signals are used and no electric signals are present. Therefore, the optical information from the optical fiber can be exchanged as it is.

The first embodiment shown in FIG. 1 and the second embodiment shown in FIG.
In comparison with the first embodiment, in the first embodiment shown in FIG. 1, a periodic filter 21 is provided after the k × m coupler 20. In this arrangement, since the wavelengths of adjacent optical cells are close to each other, crosstalk (mutual interference) may occur. However, since the wavelength range can be narrowed, the load on the wavelength tunable diode 42 is reduced.

On the other hand, in the second embodiment shown in FIG. 2, k ×
A bandpass filter 24 is provided after the m coupler 20. In this embodiment, since the wavelength range is wide, it is difficult for crosstalk to occur.
Will increase the burden.

FIG. 7 shows an output interface module (OIM) 25 commonly used in the block diagrams of the third and fourth embodiments shown in FIGS. 3 and 4.
It is a figure which shows the concrete structure of.

The output interface module 25 has an optical / electrical converter (O / E) 251 for each outgoing line.
And an electrical / optical converter (E / O) 252 set. When optical / electrical-electrical / optical conversion is performed by a set of the optical / electrical converter (O / E) 31 and the electric / optical converter (E / O) 32, the electric / optical converter (E / E / E) is used. From O) 32, all optical cells having the same wavelength λ 0 can be obtained.

In the system thus constructed,
Similar to the embodiment shown in FIG. 1, in the embodiment shown in FIGS. 3 and 4, the optical self-routed optical cell is a bandpass filter 24 (see FIG. 3) or a periodic filter 21.
(See FIG. 4), all are converted to the same wavelength .lambda.0 by the output interface module 25, and output from the output line. By making the wavelengths of the optical cells from the respective outgoing lines the same, there are the following advantages.

Since they all have the same wavelength, they are easy to handle.

The optical signal fluctuates according to the wavelength while being transmitted, but if all the signals have the same wavelength, the fluctuations become similar, and it is easy to take measures against the fluctuation.

Also in this embodiment, the k × m coupler 2
From 0 onward, all are optical signals only, and there is no interposition of electrical signals. Therefore, the optical information from the optical fiber can be exchanged as it is. Moreover, since the output can be taken out by the optical cell having the same wavelength, it is easy to handle.

FIG. 8 is a detailed operation explanatory diagram of the first embodiment of the present invention shown in FIG. The same parts as those shown in FIG. 1 are designated by the same reference numerals and symbols. In the description here, the number of incoming lines is 4, the number of outgoing lines is 4, and the delay element 22 is composed of a fiber delay line, and the maximum delay time is 5
An optical cell, that is, a structure having 5T.

Now consider a case where four optical cells arrive at each of the four incoming lines at the same time, and three optical cells arrive at the next time slot. The first optical cell that arrived is A, B, C,
Let D be the optical cell that arrived next, be E, F, and G.

These optical cells A, B, C, D, E, F, G
The wavelengths assigned to each are as shown in FIG. This is shown on the wavelength axis as shown in FIG. That is, the optical cell A has the wavelength λ13, the optical cell B has the wavelength λ14, and the optical cell C has the wavelength λ14.
To the optical cell D, the wavelength λ20 to the optical cell D, the wavelength λ1 to the optical cell E, the wavelength λ2 to the optical cell F, and the wavelength λ3 to the optical cell G.

As shown in FIG. 8, the periodic filter 21 allows the first stage to pass the optical cells having the wavelengths λ1, λ7, λ13 and λ19 and the second stage to transmit the light having wavelengths λ2, λ8, λ14 and λ20. Pass the cell. Furthermore, the third stage has wavelengths λ3, λ9, and λ1.
Pass the optical cell of 5, λ21, and the fourth stage has wavelengths λ4, λ1
Pass the optical cells of 0, λ16, and λ22, and the fifth stage has a wavelength of λ5.
, .Lamda.11, .lamda.17, .lamda.23, and the sixth stage allows the sixth stage to pass light cells having wavelengths .lamda.6, .lamda.12, .lamda.18, .lamda.24.

In the fiber delay line 22, the second stage delays one optical cell by 1T, the third stage delays two optical cells by 2T, the fourth stage delays three optical cells, the fifth stage delays four optical cells, and six. The step is delayed by 5 light cells.

Further, in the bandpass filter 24, the first stage passes the optical cells of wavelengths λ1 to λ6, and the second stage passes the wavelength λ.
Pass the optical cell of 7 to λ12, and the third stage has wavelengths λ13 to λ18.
The optical cells of the wavelengths λ19 to λ24 are passed through the fourth stage.

In the above setting, the flow of the optical cell A will be described first. The optical cell A is converted into a wavelength λ13 by the input interface module 10 and output. Then, it passes through the k × m coupler 20, passes through the first-stage periodic filter 21, and enters the m × k coupler 23 without being delayed by the fiber delay line 22. Then, the wavelength λ
It is output to the output line through the third-stage bandpass filter 24 having a pass band of 13 to λ18.

Next, the flow of the optical cell B will be described.
The optical cell B is converted into a wavelength λ14 by the input interface module 10 and output. And k × m coupler 2
After passing through 0, it passes through the second-stage periodic filter 21, is delayed by 1T for one optical cell by the fiber delay line 22, and enters the m × k coupler 23. Further, the bandpass filter 2 of the third stage
It goes through 4 and is output to the outgoing line. As a result, the flow of the light cells on the output line of the third stage is in the order of A and B.

Next, the flow of the optical cell C will be described.
The optical cell C is converted into a wavelength λ19 by the input interface module 10 and output. And k × m coupler 2
After passing through 0 through the first-stage periodic filter 21, the m × k coupler 23 is not delayed by the fiber delay line 22.
to go into. Next, 4 having a pass band of wavelengths λ19 to λ24
It passes through the band pass filter 24 of the stage and is output to the output line.

Next, the flow of the optical cell D will be described.
The optical cell D is converted into a wavelength λ20 by the input interface module 10 and output. And k × m coupler 2
After passing through 0, the signal passes through the second-stage periodic filter 21 and is delayed by one optical cell by the fiber delay line 22 to produce the m × k coupler 2
Enter 3. Then, it passes through the bandpass filter 24 of the fourth stage and is output to the output line. As a result, the flow of the outgoing line optical cell in the fourth stage is in the order of C and D.

Next, the flow of the optical cells E, F and G will be described. First, the optical cell E is converted into the wavelength .lambda.1 by the input interface module 10 and output. Then, through the k × m coupler 20, the first-stage periodic filter 2
1 and enters the m × k coupler 23 without being delayed by the fiber delay line 22. Then, the wavelengths λ1 to λ6
The signal is output to the output line after passing through the first-stage bandpass filter 24 having a pass band of.

Next, the flow of the optical cell F will be described.
The optical cell F is converted into a wavelength .lambda.2 by the input interface module 10 and output. And k × m coupler 2
After passing through 0, it passes through the second-stage periodic filter 21, is delayed by 1T for one optical cell by the fiber delay line 22, and enters the m × k coupler 23. Then, it passes through the bandpass filter 24 of the first stage and is output to the output line.

Next, the flow of the optical cell G will be described.
The optical cell G is converted into a wavelength .lambda.3 by the input interface module 10 and output. And k × m coupler 2
After passing through 0, it passes through the third-stage periodic filter 21, is delayed by 2 optical cells by 2T by the fiber delay line 22, and enters the m × k coupler 23. Then, similarly, the light passes through the bandpass filter 24 of the first stage and is output to the output line.

As a result, the flow of the optical cells on the outgoing line of the first stage is in the order of E, F, and G. The leading optical cell E is output at the same phase (timing) as the optical cells B and D that have been delayed by 1T for one optical cell among the optical cells previously input.

11 to 13 are diagrams for explaining the operation of the second embodiment of the present invention shown in FIG. The same parts as those in FIG. 2 are designated by the same reference numerals. In this example, the positions of the periodic filter 21 and the bandpass filter 24 are opposite to those of the example shown in FIGS. 8 to 10, but the other configurations are the same.

Therefore, as in FIG. 8, with four lines of incoming lines, four lines of outgoing lines, and a delay time of 5 optical cells (5T), four optical cells arrive simultaneously from each incoming line, and the next time is reached. It shows a case where three optical cells arrive at a slot at the same time.

The first arriving optical cell is A, B, C, D,
The optical cells that arrive next are designated as E, F, and G. The wavelengths assigned to these optical cells are as shown in FIG. This is shown on the wavelength axis as shown in FIG. That is, the optical cell A has the wavelength λ3, the optical cell B has the wavelength λ7, and the optical cell C has the wavelength λ7.
To the optical cell D, the wavelength λ8 to the optical cell E, the wavelength λ5 to the optical cell F, and the wavelength λ9 to the optical cell G.

In the bandpass filter 24, the first stage passes the optical cells having the wavelengths λ1 to λ4, and the second stage passes the wavelengths λ5 to λ4.
8th optical cell, the third stage passes optical cells with wavelengths λ9 to λ12, the fourth stage passes optical cells with wavelengths λ13 to λ16, and the fifth stage passes optical cells with wavelengths λ17 to λ20. Pass through, 6
The steps are set so as to pass the optical cells of wavelengths λ21 to λ24.

In the fiber delay line 22, the second stage delays the first optical cell 1T, the third stage delays the second optical cell 2T, and the fourth stage delays the third stage.
The optical cell 3T is delayed, the fifth stage is delayed by 4 optical cells 4T, and the sixth stage is delayed by 5 optical cells 5T.

The periodic filter 21 has a wavelength λ1 at the first stage.
, .Lamda.5, .lamda.9, .lamda.13, .lamda.17, .lamda.21, and the second stage is wavelengths .lamda.2, .lamda.6, .lamda.10, .lamda.14, .lamda.18, .lamda.22.
Through the optical cell at the third stage and the third stage has wavelengths λ3, λ7, λ11,
Pass the optical cells of λ15, λ19, and λ23, and the fourth stage has the wavelength λ
The optical cells of 4, λ8, λ12, λ16, λ20, and λ24 are set to pass through.

In this structure, first, the optical cell A
The flow of is explained. The optical cell A is converted into a wavelength .lambda.3 by the input interface module 10 and output. Then, after passing through the k × m coupler 20 and the bandpass filter 24 in the first stage, the light enters the m × k coupler 23 without being delayed by the fiber delay line 22. Then, it passes through the third-stage periodic filter 24 and is output to the output line.

Next, the flow of the optical cell B will be described.
The optical cell B is converted into a wavelength .lambda.7 by the input interface module 10 and output. And k × m coupler 2
After passing through 0, the signal passes through the second-stage bandpass filter 24, is delayed by 1 optical cell 1T by the fiber delay line 22, and is m × k.
Enter the coupler 23.

Then, it passes through the third-stage periodic filter 21 and is output to the output line. As a result, the flow of the outgoing line optical cell in the third stage is in the order of A and B.

Next, the flow of the optical cell C will be described.
The optical cell C is converted into a wavelength .lambda.4 by the input interface module 10 and output. And k × m coupler 2
After passing through 0, the signal passes through the first-stage bandpass filter 24 and enters the m × k coupler 23 without being delayed by the fiber delay line 22. Then, the light passes through the fourth-stage periodic filter 21 and is output to the output line.

Next, the flow of the optical cell D will be described.
The optical cell D is converted into a wavelength .lambda.8 by the input interface module 10 and output. And k × m coupler 2
After passing through 0, the signal passes through the bandpass filter 24 in the second stage, is delayed by 1T for one optical cell by the fiber delay line 22, and is m ×
Enter the k coupler 23. Then, the light passes through the fourth-stage periodic filter 21 and is output to the output line. As a result, the flow of the light cells on the outgoing line of the fourth row is in the order of C and D.

Next, the flow of the optical cells E, F and G will be described. First, the optical cell E is converted into a wavelength .lambda.1 by the input interface module 10 and output. And
First stage band pass filter 24 via k × m coupler 20
And enters the m × k coupler 23 without being delayed by the fiber delay line 22. Then, it passes through the first-stage periodic filter 21 and is output to the output line.

Next, the flow of the optical cell F will be described.
The optical cell F is converted into a wavelength .lambda.5 by the input interface module 10 and output. And k × m coupler 2
After passing through 0, the signal passes through the bandpass filter 24 in the second stage, is delayed by 1T for one optical cell by the fiber delay line 22, and is m ×
Enter the k coupler 23. Then, it passes through the first-stage periodic filter 21 and is output to the output line.

Next, the flow of the optical cell G will be described.
The optical cell G is converted into a wavelength .lambda.9 by the input interface module 10 and output. And k × m coupler 2
After passing through 0, it passes through the bandpass filter 24 of the third stage, is delayed by 2T for 2 optical cells by the fiber delay line 22, and is m × k.
Enter the coupler 23. Next, the first stage periodic filter 2
It goes through 1 and is output to the outgoing line.

As a result, the flow of the optical cells on the outgoing line of the first stage is in the order of E, F, and G. The optical cell E at the head is output at the same phase (timing) as the optical cells B and D that are delayed by one optical cell among the optical cells that were previously input.

The description of the above embodiments is based on the present invention as an ATM.
The case of applying to exchange was explained. However, the present invention is not limited to this, and is applicable to the synchronous transfer mode (STM) as well.

The configuration and operation when the present invention is applied to the STM exchange system will be described below.

FIG. 14 is another concrete example of the input interface module (IIM) 10 when it is commonly used in the case where it is configured as an optical STM (synchronous transfer mode) switching system in the configuration block diagrams of the above respective embodiments. It is a figure which shows a dynamic structure.

In the figure, the input interface module 10 receives k optical cell inputs and performs wavelength conversion of each input, so that the wavelength conversion units 40 and 40 are provided for each incoming line. The signal processing unit 45, the drive circuit 46, and the synchronization circuit 47 for controlling the operation of the above are included.

The wavelength conversion section 40 includes an optical / electrical converter (O /
E) 41, a wavelength tunable laser diode (LD) 42, and a modulator 43. As the material of the modulator 43, for example, LiNbO ₃ (LN) or the like is used.

With reference to FIG. 15, the operation when the above-described first embodiment is the optical STM (synchronous transfer mode) switching system having the input interface module 10 configured as described above will be described with reference to FIG. The explanation is as follows.

When the time slot group of the optical signal of wavelength λ 0 arrives at the input interface module 10 from each incoming line, the input interface module 10
The optical / electrical converter 41 converts an optical signal into an electric signal. The time slot group of the optical signal converted into the electric signal is input to the signal processing unit 45.

The signal processing unit 45 determines the outgoing line of each time slot according to the time slot position of the input optical signal, and further, there is no time slot output at the same time slot position of the same outgoing line. Take control.

When the output line is determined, the signal processing unit 45 controls the drive circuit 46 to drive the wavelength tunable laser diode 42 of each wavelength conversion unit 40 to emit light at a wavelength corresponding to the output line and the time slot position. . Tunable laser diode 4
The emitted light of 2 enters the subsequent modulator 43, and the driving circuit 46
The signal is modulated according to the input signal by the control of.

Here, the synchronizing circuit 47 controls the signal processing section 45 and the driving circuit 46 to operate in synchronization with each other with the input signal as a reference.

FIG. 15 (1) shows a case where the configuration of FIG. 14 is used as the input interface module 10.
FIG. 3 is a block diagram showing a configuration of an optical switching system, particularly, an STM switching system corresponding to FIG. It is configured to have three inputs and three outputs.

FIG. 15B shows three frames of input signals which are input in parallel in synchronization with the three input lines. Further, FIG. 15C shows three output signals corresponding to this input, which are output in synchronization with each other.

In FIG. 15 (2), the first frame signal input to the first input line of the three input lines is composed of time slots A1 to A4, and similarly input to the second input line. The two-frame signal is composed of time slots B1 to B4, and the third frame signal input to the third input line is composed of time slots C1 to C4.

When such a input is output from the bandpass filter 24, the wavelengths assigned to the respective time slots are arranged on the wavelength axis as shown in FIG. 15 (4).

That is, the time slots A1 to A4 carried in the first frame # 1 have wavelengths λ11 and λ, respectively.
Time slots B1 to B4 to which 1, λ6 and λ6 are assigned and which are placed in the second frame # 2 are assigned time slots λ6, λ11, λ5 and λ2, and which are placed in the third frame # 3. Wavelengths .lambda.10, .lambda.3, .lambda.1 and .lambda.10 are assigned to C1 to C4, respectively.

As shown in FIG. 15 (1), the periodic filter 21 allows the first stage to pass the time slots of wavelengths λ1, λ5 and λ9 and the second stage to pass the time slots of wavelengths λ2, λ6 and λ10. Pass through. Furthermore, the third stage has a wavelength of λ3.
, .Lamda.7, .lamda.11 time slots and the fourth stage allows wavelengths .lamda.4, .lamda.8, .lamda.12 time slots to pass.

The fiber delay line 22 is set so that the first stage delays the delay amount to 0, the second stage delays one time slot, the third stage delays two time slots, and the fourth stage delays three time slots.

Further, in the bandpass filter 24, the first stage passes the time slots of wavelengths λ1 to λ4, the second stage passes the time slots of wavelengths λ5 to λ8, and the third stage passes the wavelengths of λ9 to λ12. It is set to pass a timeslot.

In the above setting, first, the flow of the first time slot A1 of the first frame # 1 will be described. The time slot A1 is converted into the wavelength λ11 by the input interface module 10 and output.
Then, it passes through the 3 × 4 coupler 20 and the third stage periodic filter 21, is delayed by 2 time slots by the fiber delay line 22, and enters the 4 × 3 coupler 23.

Then, the light passes through the third stage band pass filter 24 having a pass band of wavelengths λ9 to λ12 and is output to the output line. As a result, the time slot A1 is arranged in the third time slot of the third frame # 3.

Next, the flow of the second time slot A2 of the first frame # 1 will be described. The time slot A2 is converted into a wavelength λ1 by the input interface module 10 and output. And a 3 × 4 coupler 20
After passing through the first-stage periodic filter 21, it enters the 4 × 3 coupler 23 without being delayed by the fiber delay line 22. Further, it passes through the bandpass filter 24 of the third stage and is output to the output line. As a result, the time slot A2 is
It is arranged in the second time slot of the first frame # 1.

Similarly, the other time slots A3 to A4 of the first frame # 1, the time slots B1 to B4 of the second frame # 2, and the time slot C of the third frame # 3.
Input interface module 1 for 1 to C4
It is converted to a predetermined wavelength at 0, passes through the synchronous filter 21, the fiber delay line 22 and the bandpass filter 24 and is output to the output line.

As a result, each optical cell is arranged at the time slot position of a predetermined frame as shown in FIG. 15 (3).

FIG. 16 shows an operation when the second embodiment is an optical STM (synchronous transfer mode) switching system having the input interface module 10 configured as shown in FIG. It is a figure explaining.

FIG. 16 (1) shows a configuration of FIG. 2 using the configuration of FIG. 14 as the input interface module 10.
FIG. 3 is a block diagram showing a configuration of an optical switching system, particularly, an STM switching system corresponding to FIG. It is configured to have three inputs and three outputs.

FIG. 16B shows the input signals of three frames which are input in parallel in synchronization with the three input lines. Further, FIG. 16 (3) shows three output signals corresponding to this input, which are output in synchronization with each other.

In FIG. 16 (2), the first frame signal input to the first input line of the three input lines is composed of time slots A1 to A4, and is similarly input to the second input line. The two-frame signal is composed of time slots B1 to B4, and the third frame signal input to the third input line is composed of time slots C1 to C4.

When such a input is output from the bandpass filter 24, the wavelengths assigned to the respective time slots are arranged on the wavelength axis as shown in FIG. 16 (4).

That is, the time slots A1 to A4 carried in the first frame # 1 have wavelengths λ9 and λ, respectively.
Time slots B1 to B4 to which 1, λ5 and λ5 are assigned and which are placed in the second frame # 2 are assigned time slots λ5, λ9, λ3 and λ4 and which are placed in the third frame # 3. Wavelengths λ6, λ7, λ1, and λ6 are assigned to C1 to C4, respectively.

The bandpass filter 24 is shown in FIG.
As shown in, the first stage passes the time slots of wavelengths λ1 to λ3, the second stage passes the time slots of wavelengths λ4 to λ6, and the third stage passes the time slots of wavelengths λ7 to λ9. The fourth stage is set to pass the time slots of wavelengths λ10 to λ12.

The fiber delay line 22 is set so that the first stage delays the delay amount to 0, the second stage delays one time slot, the third stage delays two time slots, and the fourth stage delays three time slots.

Further, in the periodic filter 21, the first stage passes the time slots of wavelengths λ1, λ4, λ7 and λ10 and the second stage passes the time slots of wavelengths λ2, λ5, λ8 and λ11. Furthermore, the third stage has wavelengths λ3, λ6, λ
The transmission characteristics are set so as to pass the time slots of 8, λ9, and λ12.

In the above setting, first, the flow of the first time slot A1 of the first frame # 1 will be described. The time slot A1 is converted into a wavelength .lambda.9 by the input interface module 10 and output.
Then, after passing through the 3 × 4 coupler 20 and the bandpass filter 24 of the third stage, it is delayed by 2 time slots by the fiber delay line 22 and enters the 4 × 3 coupler 23.

Then, the light passes through the third-stage periodic filter 21 having a pass band of wavelengths λ9 to λ12 and is output to the output line. As a result, the time slot A1 is arranged in the third time slot of the third frame # 3.

Next, the flow of the second time slot A2 of the first frame # 1 will be described. The time slot A2 is converted into a wavelength λ1 by the input interface module 10 and output. And a 3 × 4 coupler 20
After passing through the bandpass filter 24 of the first stage, it enters the 4 × 3 coupler 23 without being delayed by the fiber delay line 22. Further, it passes through the first-stage periodic filter 21 and is output to the output line. As a result, the time slot A2 is arranged in the second time slot of the first frame # 1.

Similarly, the other time slots A3 to A4 of the first frame # 1, the time slots B1 to B4 of the second frame # 2, and the time slot C of the third frame # 3.
Input interface module 1 for 1 to C4
When the wavelength is converted to a predetermined wavelength by 0, the bandpass filter 2
4, it passes through the fiber delay line 22 and the synchronous filter 21, and is output to the output line.

As a result, each time slot is represented in FIG.
As shown in (3), it is arranged at the time slot position of a predetermined frame.

In the present invention, the numbers of the periodic filters 21, the fiber delay lines 22 and the bandpass filters 24 used in the above description are not limited to the numbers shown in the embodiment, but any number of periodic filters can be used. 21, fiber delay line 2
2. The band pass filter 24 can be used. Furthermore, it is still not possible to use an arbitrary band as the wavelength band.

[0137]

As described above in detail with reference to the embodiments, according to the present invention, only passive elements are used other than the input interface module, no control is required, and synchronization can be achieved. Is not necessary.

Therefore, stable operation can be performed at high speed, and power consumption is low. In addition, a non-blocking switch configuration that does not require a control circuit is possible in one stage, which greatly contributes to improving the performance of the optical switching system.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 is a block diagram of a third embodiment of the present invention.

FIG. 4 is a block diagram of a fourth embodiment of the present invention.

FIG. 5 is a block diagram of a fifth embodiment of the present invention.

FIG. 6 Input Interface Module (IIM)
It is a figure which shows the structural example.

FIG. 7 Output Interface Module (OIM)
It is a figure which shows the structural example.

FIG. 8 is a specific operation explanatory diagram of the first embodiment.

9 is an explanatory diagram of wavelengths assigned to optical cells in FIG. 8;

FIG. 10 is an explanatory diagram (Part 1) of wavelength allocation of the optical cell indicated by the wavelength axis.

FIG. 11 is a specific operation explanatory diagram of the second embodiment.

12 is an explanatory diagram of wavelengths assigned to optical cells in FIG. 11. FIG.

FIG. 13 is an explanatory diagram (Part 2) of wavelength allocation of the optical cell indicated by the wavelength axis.

FIG. 14: Input interface module (II
It is a figure which shows the other structural example of M).

FIG. 15 is a specific operation explanatory diagram in which the STM exchange system according to the first embodiment is used.

FIG. 16 is a specific operation explanatory diagram of the STM exchange system according to the second embodiment.

FIG. 17 is a diagram illustrating a configuration example of a conventional system.

FIG. 18 is a diagram illustrating another configuration example of the conventional system.

[Explanation of symbols]

 10 Input Interface Module 20 k × m Coupler 21 Periodic Filter 22 Fiber Delay Line 23 m × k Coupler 24 Bandpass Filter 40 Wavelength Converter 41 Optical / Electrical Converter 42 Variable Wavelength LD 43 Optical Modulator 44 Delay Circuit 45 Signal Processing unit 46 Drive circuit 47 Synchronous circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H04Q 3/52 101 Z 9566-5G B 9566-5G

Claims (10)

[Claims] 1. An input interface module that receives k optical input cells and performs wavelength conversion of each optical input cell, and an output of the input interface module,
k × m couplers for converting to m outputs, m periodic filters that receive respective outputs of the k × m couplers and allow only cells having a wavelength of a constant period to pass, and the m periodic filters Receiving each output of the filter, (m-1)
M delay elements that give a delay amount of T (T is a time slot of an optical cell), m × k couplers that receive the outputs of the m delay elements and convert them into k outputs, An optical time-division switching system having k band-pass filters that receive each output of an m × k coupler and pass only cells having a wavelength in a predetermined band. 2. An input interface module that receives k optical input cells and performs wavelength conversion of each optical input cell, and an output of the input interface module,
k × m coupler for converting to m outputs, m bandpass filters for receiving respective outputs of the k × m coupler and passing only cells having wavelengths in a predetermined band, and m bandpass filters Each output of (m-
1) m delay elements that give a delay amount of T (T is a time slot of an optical cell), and an m × k coupler that receives each output of the m delay elements and converts the output into k outputs An optical time division switching system having m periodic filters which receive each output of the m × k coupler and pass only cells having a wavelength of a constant period. 3. The structure according to claim 1, further comprising an output interface module that receives each output of the k bandpass filters and converts all cells of respective wavelengths into cells of the same wavelength. Optical ATM switching system. 4. The structure according to claim 2, further comprising an output interface module which receives each output of the m periodic filters and converts all cells of respective wavelengths into cells of the same wavelength. Optical time division switching system. 5. The k × 1 coupler and the 1 × m coupler connected through an optical amplifier instead of the k × m coupler, and the optical amplifier instead of the m × k coupler according to claim 1. An optical time division switching system comprising at least one of an m × 1 coupler and a 1 × k coupler connected via an optical time division switching system. 6. The optical time division switching system according to claim 1, wherein the delay element is composed of a fiber delay line. 7. The input interface module according to claim 1, further comprising a wavelength conversion unit provided for each input line, and a signal processing unit controlling each operation of the wavelength conversion unit. An optical time division switching system characterized by being configured as follows. 8. The optical time division switching system according to claim 7, wherein the wavelength conversion unit converts into a predetermined wavelength corresponding to a predetermined outgoing line and a delay amount for each optical input cell. 9. The optical time division switching system according to claim 8, wherein the wavelength of the optical input cell is converted for each time slot. 10. The optical time division switching system according to claim 8, wherein a frame is composed of a plurality of cells, and wavelength conversion is performed on each of the plurality of cells for each frame.