JP2874540B2 - Optical ATM 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 ATM switch.

In broadband ISDN, high-speed data is transmitted from a telephone,
It is necessary to efficiently provide various services up to image signals. Research and development of ATM exchange is actively being carried out as an exchange method for this purpose. At present, some ATM exchanges have started to use LSI-type electronic switches, but with the aim of further increasing the capacity in the future, studies on optical ATM switches using optical switching technology have begun. ing.

[0003] ATM switches are classified into input buffer, output buffer, shared buffer, and cross point buffer according to the position of the buffer memory in the switch. Among them, the output buffer method is excellent in that control is not so complicated and a large throughput can be obtained.

[0004]

2. Description of the Related Art FIG. 5 is a block diagram showing an output buffer type ATM switch using a conventional optical switching technique. Regarding this conventional example,
EE Journal of Selected Elias in Communications (IEEE Journal)
al of Selected Areas in C
Ommunications), Vol. 8, No. 6, 19
Details of the paper published on pages 990 to 1004 in 1990. Optical transmitters 3-1 to 3-m having mutually different output wavelengths are connected to the input terminals 1-1 to 1-m of the electric cell signals. It is converted into an optical signal having a different wavelength for each input unit and output. Each optical signal is multiplexed / branched by the m × m star coupler 11 and sent to a plurality of output units. Demultiplexer 1 at each output
The signals of the respective wavelengths are separated by 0-1 to 10-m, converted into electric signals by the optical receivers 7-1 to 7-m, and then stored in the buffer memories 8-1 to 8-m. According to this configuration, all the input signals can be led to the buffer memory placed on the output side without any collision, whereby an output buffer type optical ATM switch can be realized.

[0005]

However, in such a conventional optical ATM switch, each output unit needs to have an optical receiver and a buffer memory corresponding to the number of input ports, and the amount of hardware is very large. There is a problem to say.

An object of the present invention is to provide an output buffer type optical ATM switch that can be realized with a small amount of hardware.

[0007]

In the optical ATM switch according to the present invention, m and n are natural numbers, and m number of judgments are performed to judge the destination addresses of m cell signals input in time synchronization with each other. A circuit, m optical transmitters for converting the input cell signal into optical signals, and m optical switches for inputting the outputs of the m optical transmitters and switching connections based on the determination result in the address determination circuit. , 1-input n-output (1 × n) optical switches, and i of each of the m 1 × n optical switches
N (m = 1) optical switches for inputting the (i = 1 to n) th output, an optical receiver and a buffer memory connected to the outputs of the n m × 1 optical switches, The control section controls the connection state of the optical switch. The control section controls the connection states of the m input signals of the n m × 1 optical switches to the output terminals by one of the input signals synchronized with each other.
It is characterized by being driven so as to be continuously switched in units of minislots in which the bit is reduced to 1 / m.

Further, the optical ATM switch according to the present invention comprises:
With m and n being natural numbers, m determination circuits for determining the destination addresses of the m cell signals input in time synchronization with each other, and the wavelength of the output optical signal according to the determination result of the determination circuit M optical transmitters that tune to a wavelength corresponding to a desired output port and convert a cell signal into an optical signal; and output light signals of the m optical transmitters and n output ports M optical demultiplexing circuits for outputting an optical signal to a port corresponding to the wavelength of an input signal, and n optical demultiplexing circuits for inputting the i-th (i = 1 to n) outputs of the m optical demultiplexing circuits, respectively. An m × 1 optical switch, an optical receiver and a buffer memory connected to the outputs of the n m × 1 optical switches, and a control unit for controlling a connection state of the m × 1 optical switch. The m input signals of the n m × 1 optical switches Connection to the output terminal, and wherein the driven it to switch the 1-bit input signal in synchronization with each other continuously at minislot units was 1 m minutes.

Further, in the optical ATM switch according to the present invention, the control unit causes the n m × 1 optical switches to divide one bit of the input signal synchronized with each other by a factor of r.
(Where r is a natural number and m> r)
The input port for which the input signal is determined to be present based on the determination result of the address determination circuit is given a predetermined priority.
Characterized in that it is driven to switch continuously in order based on the order position.

[0010]

The m × 1 optical switch according to the present invention has a function of time-division multiplexing m input optical signals at the optical signal level, increasing the signal speed, and bundling the signals into one to output. Therefore, the number of optical receivers and buffer memories to be prepared on the output side can be reduced.

[0011]

The present invention will be described below in detail with reference to examples.

FIG. 1 is a block diagram of a first embodiment of the optical ATM switch according to the present invention. The m input terminals 1-1 to 1-m are connected to m determination circuits 2-1 to 2-m for determining a destination address of a cell signal, and a desired destination of each cell is decoded. . Each cell signal is then transmitted to the optical transmitter 3-
It is converted into an optical signal by 1-3-m and output. 1 × n optical switches 4-1 to 4-m are connected to the end of each optical transmitter. The output terminals of the 1 × n optical switches 4-1 to 4-m are connected to the i-th (i = 1 to 1) of each 1 × n switch.
n) m × 1 optical switches 5-1 to which the output of n) is input
5-m is connected. n m × 1 optical switches 5-
1 to 5-n are driven by the control unit 6. Further, the outputs of these n m × 1 optical switches are connected to the optical receivers 7-1 to 7-1.
7-n and the buffer memories 8-1 to 8-n are connected.

Next, the operation of the optical ATM switch will be described. Time-synchronized cell signals are input as electric signals to the m input terminals 1-1 to 1-m, respectively. The desired destination of each cell signal is decoded by the determination circuits 2-1 to 2-m. Each cell signal is then transmitted to the optical transmitters 3-1 to 3-m
Is converted into an optical signal and output. The 1 × n switches 4-1 to 4-m connected to the ends of the respective optical transmitters connect the input signal to a desired one of n output terminals based on the determination result of the determination circuit. This connection state is synchronized with the cell.
Retained for the cell duration.

Next, the operation of the m × 1 optical switches 5-1 to 5-m will be described. FIG. 2 is a diagram for explaining the operation of the m × 1 optical switch 5. The figure shows the state of the input / output signals of one m × 1 optical switch 5, where m = 4 for simplicity, and a cell is input to the third input terminal depending on the connection state of the 1 × n optical switch. No state is shown. mx1
The optical switch is driven by the control unit 6 so as to be continuously switched in units of minislots in which one bit of the input signal is reduced to 1 / m. Therefore, the m × 1 optical switch outputs all input signal information without loss, but the number of output signals is bundled into one.

Referring back to FIG. 1, the output terminals of the m × 1 optical switches 5-1 to 5-n are connected to the optical receivers 7-1 to 7-1.
7-n are installed, and the optical signal is converted into an electric signal. This signal is stored in the buffer memories 8-1 to 8-n. m
Since the output signals are bundled by the × 1 optical switch, it is sufficient to provide one optical receiver for each m × 1 optical switch, and the amount of hardware is greatly reduced.

Here, assuming that the speed of the cell signal input to each input port is 1.2 Gb / s and the number of input ports is 8, the signal speed at the output of the m × 1 optical switch is 10 Gb.
/ S. It has been reported that the operation speed of the optical switch is about several tens Gb / s or more, and there is no problem in the operation of the m × 1 optical switch. Further, the m × 1 optical switch is a device that performs a simple operation of sequentially connecting m inputs to one output terminal, so that control is very easy. 10 optical receivers
A device operating at Gb / s has been realized, and there is no problem in its feasibility. 10 Gb / s for buffer memory
May be stored as it is, or may be stored once after being developed into a parallel signal to reduce the signal speed.

1 × from the input of the optical switch according to the invention
The portion up to the n optical switch can be realized by the embodiment as shown in FIG. In this configuration, an optical transmitter 9 whose output wavelength is variable is connected behind the determination circuit 2 connected to the input terminal 1, and the wavelength of the optical signal to be output is set to a desired output port according to the determination result of the determination circuit 2. The cell signal is converted into an optical signal by tuning to a wavelength corresponding to the wavelength. An optical demultiplexing circuit 10 is connected to the output of the variable wavelength optical transmitter 9, and the function of a 1 × n optical switch is realized by the principle of wavelength routing.

In the above embodiment, each output section of each m × 1 optical switch has a buffer memory capable of coping with a case where all input cells are concentrated on one output terminal. However, the probability that such a state will occur is extremely low statistically, and the amount of hardware of the buffer memory on the output side of the optical switch can be reduced while keeping the cell loss rate at a practically low value.

FIG. 4 is a diagram for explaining an embodiment in which the m × 1 optical switch 5 is driven by a different method in the optical ATM switch according to the present invention. Here, m = 8 and 1
A state in which no cell is input to the second, third, fourth, fifth, and sixth input terminals according to the connection state of the × n optical switch is shown. In this embodiment, the m × 1 optical switch is one of the input signals.
Driving is performed in units of minislots in which the bit is set to 1 / r (r is a natural number and m> r). r is mx
This value corresponds to the number of signals simultaneously extracted from one optical switch, and is set to a value that sufficiently reduces the cell discard rate in consideration of the traffic state. Here, the description will be made on the assumption that r = 4.

It is determined from the results of the determinations by the determination circuits 2-1 to 2-m that no cell is input to the second, third, fourth, fifth and sixth input terminals of the m × 1 optical switch. Priority between 1, 7, 8-th input with cell input is predetermined by a separate control, it is assumed that in the order of 1,8,7. In this case, in the mx1 optical switch 5, the control unit 6 controls the first three slots in units of minislots obtained by dividing one bit into four so that input signals are connected to the output terminals in the order of 1, 8, and 7. Driven. Since there is no signal to be selected in the fourth mini slot, the optical switch is in the non-selected state. By performing such an operation, it is possible to suppress an increase in the signal speed at the output section of the mx1 optical switch 5, and
The amount of hardware in the buffer memory can also be reduced. Here, the number of cells simultaneously input to the m × 1 optical switch is r
Has been described an example in less than, if the number of cells becomes more than r, the signal from the lower input terminal of priority are discarded without being selected by the m × 1 switch. Although it is necessary to set the value of r as this situation does not occur, even if the if rarely such a state occurs, from which input port the determining circuit and a preset priority It is possible to know whether or not the signal has been discarded, so that retransmission or non-delivery notification can be controlled.

[0021]

As described above, according to the present invention, an output buffer type optical ATM switch can be realized with a small amount of hardware.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the m × 1 optical switch of the present invention.

FIG. 3 is a block diagram illustrating an embodiment of a 1 × n optical switch according to the present invention.

FIG. 4 is a diagram for explaining the operation of the m × 1 optical switch of the present invention.

FIG. 5 is a block diagram for explaining a conventional optical ATM switch.

[Explanation of symbols]

 1, 1-1 to 1-m input terminal 2, 2-1 to 2-m determination circuit 3-1 to 3-m optical transmitter 4-1 to 4-m 1 × n optical switch 5-1 to 5- nmx1 optical switch 6 control unit 7-1 to 7-n optical receiver 8-1 to 8-n buffer memory 9 variable wavelength optical transmitter 10, 10-1 to 10-m demultiplexing circuit 11 star coupler

Claims (3)

(57) [Claims] An m number of determination circuits for determining destination addresses of m cell signals input in time synchronization with each other, where m and n are natural numbers, and an input cell signal is converted into an optical signal. M optical transmitters to be converted, and m 1-input n-outputs (1 × n) that receive the outputs of the m optical transmitters and switch the connection based on the determination result of the address determination circuit.
An optical switch and n m × 1 inputs to each of the i-th (i = 1 to n) outputs of the m 1 × n optical switches
An optical switch, an optical receiver connected to outputs of the n m × 1 optical switches, a buffer memory connected to the optical receiver, and a control unit for controlling a connection state of the m × 1 optical switch And the control unit controls the n number of m ×
The connection state of the m input signals of the one optical switch to the output terminals is driven so as to be continuously switched in units of minislots in which one bit of the mutually synchronized input signals is reduced to 1 / m. Optical ATM switch. 2. The method according to claim 1, wherein m and n are natural numbers, and m determination circuits for determining destination addresses of m cell signals input in time synchronization with each other, and a wavelength of an output optical signal. M optical transmitters that tune to a wavelength corresponding to a desired output port according to the determination result of the circuit and convert the cell signal into an optical signal; and n optical transmitters that receive the output optical signals of the m optical transmitters as inputs. M optical demultiplexing circuits for outputting an optical signal to a port corresponding to a wavelength of an input signal among output ports;
The i-th (i = 1 to 1) of each of the m optical demultiplexing circuits
n) m × 1 optical switches for inputting the output of n), an optical receiver connected to the outputs of the n m × 1 optical switches, and a buffer memory connected to the optical receiver; The control unit controls a connection state of the m × 1 optical switch, and the control unit synchronizes a connection state of the n m × 1 optical switches to output terminals of m input signals with each other. An optical ATM switch driven so as to be continuously switched in a unit of minislot in which one bit of an input signal is reduced to 1 / m. 3. The control section causes the n m × 1 optical switches to convert one bit of an input signal synchronized with each other to r.
Min 1 (r is and m> r is a natural number) in minislots units to an input port to which the input signal is determined to exist by the judgment result of the address determination circuit, in the order based on the preset priority claim 1, characterized in driven it to switch to continuous or optical ATM switch according to claim 2.