JP3171352B2 - Optical packet selector and optical packet 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 packet selector having a high speed, a large capacity, and an excellent expandability, and an optical packet switch using the same.

[0002]

2. Description of the Related Art A configuration of a conventional packet switch using an electric signal is shown in FIG. 9 (Reference 1: H. SUZUKI, H. NAGANO,
T.SUZUKI, T.TAKEUCHI, AND S.IWASHITA, "Output-buff
er Switch Architecture or Asynchronous Transfer Mo
de, "ICC'89, 4.1, June 1989.).

In FIG. 9, 91 is an input signal line, 92 is a time division multiplexing circuit, 93 is a time division highway, 94 is an address filter circuit, 95 is a buffer memory, and 96 is an output signal line.

Hereinafter, the operation principle will be described with reference to FIG. First, when a packet signal sequence in which the number of bits of one packet is L and the time length of one packet is T is supplied to each of the n input signal lines 91, the n-sequence signal sequence is time-division multiplexed. The circuit 92 synchronizes and multiplexes one packet length into a time division highway 93 as a signal of T / n. The time-division highway 93 is constantly monitored by the address filter circuit 94, and passes only packets matching the address corresponding to each output signal line 96. Then, the packet that has passed through the address filter circuit 94 is supplied to a buffer memory (FIFO memory) 95. Each of the buffer memories 95 accumulates a signal supplied from the corresponding address filter circuit 94 and outputs the signal to the output signal line 96 as a packet having a time length T. Here, when a packet exceeding the capacity arrives at the buffer memory 95, the packet is discarded.

However, the conventional packet switch using an electric signal (output buffer type packet switch) has a simple structure, has few internal blocks, and can be added simply by adding input / output sections to both sides. However, since the signal speed on the time-division highway is limited by the operation speed of the time-division multiplexing circuit and the address filter circuit, there is a problem that a sufficient capacity cannot be obtained.

For example, if the signal speed on the time-division highway is at most 1.2 Gbit / s and the signal speed on the input / output signal line is 600 Mbit / s, only two input / output signal lines can be accommodated. The limitation is to switch eight video channels of 150 Mbit / s to two routes.
In order to increase the throughput, a method of converting the signal on each input signal line into a parallel signal having a low speed by serial / parallel conversion and multiplexing the signals on a plurality of time-division highways in parallel is conceivable. As the number of time-division multiplexing circuits and address filter circuits increases and the configuration becomes complicated, there is a problem that the advantages of the present switch are impaired.

Therefore, as means for solving the above problems, for example, an optical packet switch using an optical signal has been proposed as described in Japanese Patent Application No. 1-255043 (Document 2). This aims to increase the switch capacity by utilizing the high speed and broadband characteristics of light and the broadband characteristics of optical fibers as compared with the conventional packet switch using an electric signal.

Next, FIG. 8 shows a configuration of a conventional optical packet switch described in Japanese Patent Application No. 1-255043 (Reference 2). 8, reference numeral 81 denotes an input signal line, 82 denotes an ultrashort optical pulse oscillator, 83 denotes an optical packet modulator, 84 denotes an optical multiplexing / distributing device, 85 denotes an optical address filter, 86 denotes an optical buffer, and 87 denotes an optical packet demodulator. It is.

The operation will be described below with reference to FIG.
The n input signal lines 81 input to the n optical packet modulators 83. Each of the optical packet modulators 83 modulates an optical pulse distributed from the ultrashort optical pulse oscillator 82 with an electric packet signal transmitted through the input signal line 81 and input to the optical packet modulator 83, and then modulates the high-speed optical packet. Convert to a signal.

This high-speed optical packet signal is input to an optical multiplexing / distributing device 84, where each optical packet signal is time-division multiplexed and distributed by the same number as the number of input signals. After the distribution, the optical packet signal is input to the optical address filter 85, and the optical packet signal passes through the optical address filter 85 and is input to the optical buffer 86 only when the address of the input optical packet signal matches the output line address. In the optical buffer 86,
The time interval between the output of the input optical packet signal and the output of the next optical packet signal is T or more, and the signal is output to the optical packet demodulator 87. Here, the optical packet signal input to the optical packet demodulator 87 is converted into an electric signal having the same time length T as the packet supplied to the input signal line 81 and output.

The optical address filter 85 shown in FIG. 8 has no function of selecting an optical packet for a wavelength-multiplexed signal.

[0012]

However, in the conventional optical packet switch, there are practically difficult problems such as generation of an ultrashort optical pulse, control speed by an electric signal, synchronization technology, and the like. Has an electric packet signal 2
It is thought that the capacity will only increase by about an order of magnitude.
There is a problem that high-speed signal processing cannot be performed with a large capacity of t / s class or more.

An object of the present invention is to provide a large-capacity and high-speed optical packet switch having a Tbit / s class signal processing speed. is there.

Another object of the present invention is to provide an optical packet selector capable of collectively selecting and buffering wavelength-division multiplexed and time-division optical packet signals in an output buffer type optical switch.

Other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0016]

In order to achieve the above object, an optical packet selector according to the first aspect of the present invention comprises a plurality of optical packet selectors having different wavelengths, each of which is provided with an address of a different wavelength. An input end to which an optical packet signal wavelength-multiplexed with pulsed light is input, and a wavelength at which the input optical packet signal is demultiplexed into two components, an optical packet data signal and an optical packet address signal, and output. A demultiplexer, and an address wavelength demultiplexer that demultiplexes a sequence of optical packet address signals output from the wavelength demultiplexer by the same number as the number of the different wavelengths included in the optical packet signal, and outputs The same number of photodetectors as the number of the different wavelengths for converting an optical packet address signal output from the address wavelength demultiplexer into an electrical signal, and an optical packet data signal sequence output from the wavelength demultiplexer Different A data wavelength demultiplexer having an output end for demultiplexing and outputting the same number of wavelengths as the number of wavelengths, and a light output from the data wavelength demultiplexer in which a fixed address is previously assigned to the address filter itself. A packet data signal is detected, and the optical packet is transmitted only when the address of the address signal added to the detected optical packet data signal before being demultiplexed by the wavelength demultiplexer matches the fixed address. The same number of address filters as the number of the different wavelengths through which the data signal passes, and each of the address filters so as to avoid contention occurring when the optical packet data signal output from each of the address filters exists in the same time slot. It has the same number of input terminals and one output terminal as the number of the different wavelengths for outputting the optical packet data signal at a time interval of a predetermined time or more. A buffer, characterized by comprising an address decoder for controlling the light buffer and each of the address filters in accordance electric signal output from the photodetector.

According to the means (2) of the present invention, a plurality of signal lines for transmitting an electric packet signal sequence to which a packet has a fixed time length and the number of bits and which is given an address in advance are inputted. An optical packet switch comprising a terminal and the same number of output terminals as the number of the input terminals, wherein a signal input from one end of the input terminal is output from a predetermined end of the output terminal. An optical pulse oscillator that oscillates a light pulse of a fixed wavelength at a fixed period, and divides the oscillated light pulse into a fixed number, and outputs the light pulse. An optical pulse output from the optical pulse oscillator provided for each input signal line is modulated according to a data portion of an electric packet signal supplied through the input signal line, An optical packet signal compressed so that a packet time length is equal to the product of the one packet bit number and the one pulse time width is output at a period equal to the one packet time length, and an address portion of the electric packet signal is output. An optical packet compressor that performs laser modulation according to the following and outputs an optical packet address signal; and an optical multiplex that outputs a time-division multiplexed signal by delaying each optical packet signal of an optical packet signal sequence output from the optical packet compressor. And a plurality of optical packet transmitters comprising a plurality of optical pulse transmitters, and the same number of optical packet transmitters as the number of the optical pulse oscillators are input, and multiplexed and distributed. An optical multiplexing / demultiplexing device having the same number of input ports as the number of optical packet transmitters and an output port corresponding to the product of the number of optical packet transmitters and the time division multiplexing. The optical packet selector according to claim 1, wherein the optical packet selector has an input terminal to which an optical packet signal is input from an output port of the optical packet transmitting unit, by the number of output ports of the optical multiplexer / distributor, An optical packet signal which is installed so as to be one for each of the output ports, and whose time length outputted from the optical packet selector is equal to the product of the one packet bit number and the one pulse time width. Is provided with an optical packet decompressor for converting the signal into an electric packet signal having a time length equal to the one packet time length.

[0018]

According to the above means, in the optical packet switch, the main functions of the packet switch, such as the modulation, multiplexing, address identification, and buffering of the packet signal, are performed by utilizing the optical signal processing technology using ultrashort optical pulses. Since the ultrashort optical pulse has a very small pulse time width, the time division multiplexing of the optical packet signal can be increased, and the input signal can be wavelength-division-multiplexed by an optical multiplexer / demultiplexer. Since the number of lines can be increased by the number of wavelength division multiplexing, an optical packet switch having a switch capacity larger than that of the conventional optical packet switch can be obtained. For example, assuming that the electric processing time is 1 ns, the width of the ultrashort optical pulse is 10 ps, and the number of wavelength multiplexing is 10, the signal speed is three orders of magnitude faster than that of a conventional packet switch using electrical signals, and the switch capacity is also increased to three digits However, a signal processing speed of the Tbit / s class can be obtained.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of an optical packet selector according to the present invention, wherein 1 is a wavelength demultiplexer,
2 is an address wavelength demultiplexer, 3-i (where i is a natural number, i = 1, 2,... M) is a photodetector for converting an optical address signal into an electric signal, and 4 is an optical data signal Wavelength demultiplexers (wavelength demultiplexers for data), 5-i are address filters, 6 is an optical buffer, and 7 is an address decoder.

As shown in FIG. 1, the optical packet selector of this embodiment separates an optical packet signal into data and an address by a wavelength demultiplexer 1, and the address is demultiplexed by an address wavelength demultiplexer 2. The signals are demultiplexed into addresses corresponding to different wavelengths, respectively, detected by the photodetectors 3-1 to 3-m, and input to the address decoder 7. And these are
The address decoder 7 serves as a control signal to the address filter 5-i and the optical buffer 6. The data is demultiplexed into m lines by the data wavelength demultiplexer 4 and input to the address filters 5-i. Data is selected by the address filter 5-i according to the control signal from the address decoder 7, and the selected optical packet is input to the optical buffer 6.

With this configuration, in the output buffer type optical switch, it is possible to collectively select and buffer wavelength-division multiplexed and time-division optical packet signals.
This is particularly effective when applied to an output buffer type optical switch.

FIG. 2 is a block diagram showing the configuration of an embodiment of an optical packet switch using an optical packet selector according to the present invention. 8-ij (where j is a natural number and j = 1,
2,... N) are input signal lines, to each of which an electric signal having a low speed is supplied. 9-i is an ultrashort optical pulse oscillator, 10-ij is an optical packet compressor, 11-i is an optical multiplexer, and 12-i is an optical packet transmitting unit.
The ultrashort optical pulse oscillators 9-i of the respective optical packet transmitters oscillate at different wavelengths λi. Reference numeral 13 denotes an optical multiplexer / demultiplexer. 14-h (where h is a natural number and h =
1, 2,... Mn) are optical packet selectors. Fifteen
-h is an optical packet decompressor. In the following description, FIG.
Based on FIG. 2 and FIG. 2, the operation of the optical switch according to the present embodiment will be sequentially described.

FIG. 3 is a block diagram showing the configuration of the optical packet compressor 10-ij shown in FIG. 2, in which 16 is a data / address divider, 17 is an optical intensity modulator, and 18 is 1
(Number of inputs) × 2 (number of outputs) optical splitter, 19 is an optical fiber delay line, 20 is a 2 × 1 optical coupler, 21 is an optical gate switch, 22 is a laser diode, and 23 is an optical coupler.

The pre-addressed electric packet signal input to each optical packet compressor 10-ij via each input signal line 8-ij is converted into an address signal (time signal) by the data / address divider 16. Length T ₁ ) and a data signal (number of bits L, time length T ₂ ). After that, the pulse width t and the period T / L (however,
T = T ₁ + T ₂ , satisfying t <T / L), and when the optical pulse having the wavelength λi is supplied to the optical packet compressor 10-ij, the optical packet compressor 10-ij As shown in FIG. 3, the light pulse is modulated by the light intensity modulator 17 according to the data signal.

Further, the modulated optical pulse is passed through a circuit composed of a 1 × 2 optical branching unit 18, an optical fiber delay line 19, and a 2 × 1 optical coupler 20 in k stages. By removing the extra pulses, a high-speed optical packet consisting of 2 ^k pulses is generated (Japanese Patent Application No. Hei.
-18723).

FIG. 4 is a timing chart showing the relationship between the optical pulse in the internal circuit of the optical packet compressor shown in FIG. 3 and the control signal in the optical gate switch 21. In FIG. a) is the pulse light output from the light intensity modulator 17, (4-b) is the pulse light output from the first stage 2 × 1 optical coupler 20, and (4-c) is k.
The pulse light output from the 2 × 1 optical coupler 20 at the stage is
(4-d) indicates a control signal in the optical gate switch 21;
(4-e) shows high-speed optical packet data signals output from the optical gate switch 21 with respect to the same time axis.

On the other hand, the address signal from the data / address divider 16 is converted into an optical address signal by directly modulating the laser diode 22. The high-speed optical packet data signal and optical address signal are multiplexed by the optical coupler 23 and output from the optical packet compressor 10-ij.

As shown in FIG. 2, the optical packet compressor 10
All of the outputs from -ij are time-division multiplexed by the optical multiplexer 11-i and output from the optical packet transmitting unit. Next, the output from each optical packet transmitting unit is input to an optical multiplexer / demultiplexer, wavelength-multiplexed, distributed to mn outputs, and input to the optical packet selector 14-h.

FIG. 1 shows an optical packet selector. In the optical packet selector 14-h, the optical packet signal is split into data and an address by the wavelength splitter 1 described above, and the address is used for the address wavelength splitter. The wavelength is demultiplexed into addresses for different wavelengths by the wave detector 2, and the photodetectors 3-1 to 3-3 are respectively obtained.
−m and input to the address decoder 7. These become control signals to the address filter 5-i and the optical buffer 6 by the address decoder 7. The data is demultiplexed into m lines by the data wavelength demultiplexer 4 and input to the address filters 5-i. Address filter 5 according to a control signal from address decoder 7
Data is selected by -i, and the selected optical packet is input to the optical buffer 6.

FIG. 5 is a block diagram showing the configuration of the optical buffer 6, wherein 24 is an m × m optical switch, 25 is an optical fiber delay line group, and 26 is an m × 1 optical switch. The optical buffer 6 outputs all optical packet signals at intervals equal to or longer than the time interval T. Optical packet selector 14-h
Is output to the optical packet decompressor 15-.
h.

FIG. 6 is a block diagram showing the structure of the optical packet decompressor 15-h. Reference numeral 27 denotes a 1 × 2 optical switch, reference numeral 28 denotes an optical fiber delay line, and reference numeral 29 denotes a 2 × 1 optical coupler. , 30 is a photodetector, # 1 is a switch port for outputting to the side of the 1 × 2 optical switch 27 without the optical fiber delay line 28, and # 2 is to the side of the 1 × 2 optical switch 27 where the optical fiber delay line 28 is provided. Switch port to output. The optical packet signal input to the optical packet expander 15-h is converted into a circuit composed of a 1 × 2 optical switch 27 to which a control signal is input, an optical fiber delay line 28, and a 2 × 1 optical coupler 29. After passing through the stage, the optical packet signal having the time length Lt is converted into an electric packet signal having the time length T by being converted into an electric signal by the photodetector 30 (for details, refer to Japanese Patent Application No. 4-41106, "Optical pulse"). Interval stretcher ").

FIG. 7 is a timing chart showing the relationship between the optical pulse and the control signal to each switch 27 in the circuit shown in FIG. 6. (7-a) shows the relationship between the optical pulse and the optical packet decompressor 15-h. (7-b) is a control signal to the first stage 1 × 2 optical switch 27, (7-c) is an output light at the switch port # 1, (7-d) is a switch port # 2 (7-e) is the output light from the first-stage coupler 29, (7-f) is the control signal to the second stage 1 × 2 optical switch 27, and (7-g) is the The output light from the second-stage coupler 29 and (7-h) show the output light from the k-th coupler 29 with respect to the time axis on the horizontal axis.

From the above description of the operation, the optical packet switch of this embodiment shown in FIG. 2 can perform self-routing connection of the optical packet on the input signal line to the output signal line corresponding to each address as a packet of the same format. ×
It can be seen that the switch function of nm is accurately performed.

As can be seen from the above description, according to the optical packet switch of this embodiment, the following effects can be obtained.

That is, the pulse time width t of the ultrashort light pulse
Is very small, the degree of time division multiplexing of the optical packet signal can be increased, and further, the input signal line is multiplied by the wavelength multiplexing number of the related art by being wavelength division multiplexed by the optical multiplexer / demultiplexer 13. Therefore, an optical packet switch having a switch capacity larger than that of a conventional optical packet switch can be obtained.

For example, the switch throughput (capacity) in the optical packet switch of the present embodiment is such that a laser diode of 1.55 μm band is used for an optical data signal (ultra short optical pulse) and a laser diode of 1.3 μm band is used for an optical address signal. Assuming that a practical optical pulse width obtained from a laser diode is 10 ps, the number of wavelengths can be estimated to be about 10 from the bandwidth of an optical device (optical amplifier, switch, etc.), and the signal processing capability of several Tbit / s I can see you.

Although the present invention has been described in detail with reference to the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments and can be variously modified without departing from the scope of the invention. Absent.

[0039]

As described above, according to the optical packet switch of the present invention, the number of input signal lines can be increased because high-speed processing is performed using ultrashort optical pulses having a small pulse width. Further, by using wavelength multiplexing, Tb
It is possible to realize a large-capacity it / s optical packet switch. For example, if the 1-bit length of a conventional output buffer type packet switch using an electric signal is 1 ns, the pulse width of an ultrashort optical pulse is 10 ps, and the number of wavelengths is 10, the switch capacity can be increased by three digits.

Further, according to the optical packet selector of the present invention, in the output buffer type optical switch, the wavelength division multiplexed and time division optical packet signal can be collectively selected and buffered. And the optical packet selector can easily configure the optical packet switch of the present invention.
It is effective when applied to an output buffer type optical switch.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an optical packet selector according to an embodiment of the present invention;

FIG. 2 is a block diagram showing a configuration of an optical packet switch according to an embodiment of the present invention;

FIG. 3 is a block diagram showing a configuration of an optical packet compressor;

FIG. 4 is a timing chart showing a relationship between an optical pulse and a control signal for an optical gate switch in the optical packet compressor;

FIG. 5 is a block diagram showing a configuration of an optical buffer;

FIG. 6 is a block diagram showing a configuration of an optical packet decompressor.

FIG. 7 is a timing chart showing a relationship between an optical pulse and a control signal for an optical switch in the optical packet extender;

FIG. 8 is a block diagram showing a configuration of a conventional output buffer type optical packet switch.

FIG. 9 is a block diagram showing a configuration of a conventional output buffer type electric packet switch.

[Explanation of symbols]

1: wavelength demultiplexer, 2: wavelength demultiplexer for address, 3-i:
Photodetector, 4 ... wavelength splitter for data, 5-i: address filter, 6,86: optical buffer, 7: address decoder, 8-ij: input signal line, 9-i: ultrashort optical pulse Oscillator, 10-ij optical packet compressor, 11-i optical multiplexer, 12-i optical packet transmitter, 13 optical multiplexer / demultiplexer, 14-h optical packet selector, 15- h: optical packet decompressor, 16: data / address splitter, 17: optical intensity modulator, 18: 1 × 2 optical splitter, 19: optical fiber delay line, 20: 2 × 1 optical coupler, 21: light Gate switch,
22 laser diode, 23 optical coupler, 24 mx
m optical switch, 25 optical fiber delay line group, 26 mx
1 optical switch, 27 ... 1 × 2 optical switch, 28 ... optical fiber delay line, 29 ... 2 × 1 optical coupler, 30 ... photodetector,
81: input signal line, 82: ultrashort optical pulse oscillator, 83:
Optical packet modulator, 84: optical multiplexing / demultiplexing device, 85: optical address filter, 87: optical packet demodulator.

Claims (2)

(57) [Claims] 1. An optical packet signal having an input end to which an optical packet signal wavelength-multiplexed by a plurality of pulsed lights having different wavelengths, each having an address of a different wavelength, is inputted. And a wavelength demultiplexer for demultiplexing the two components into an optical packet data signal and an optical packet address signal and outputting the two components. An optical packet address signal output from the wavelength demultiplexer is included in the optical packet signal. An address wavelength demultiplexer for demultiplexing and outputting the same number of wavelengths as the number of different wavelengths, and the same number as the number of the different wavelengths for converting an optical packet address signal output from the address wavelength demultiplexer into an electric signal A wavelength detector for data having an output terminal for demultiplexing an optical packet data signal sequence output from the wavelength demultiplexer by the same number as the number of different wavelengths and outputting the same; A fixed address is assigned to the optical filter itself, the optical packet data signal output from the data wavelength demultiplexer is detected, and the detected optical packet data signal is demultiplexed by the wavelength demultiplexer. The address of the address signal assigned to the address filter is the same as the number of the different wavelengths that allows the optical packet data signal to pass only when the address matches the fixed address, and output from each of the address filters. In order to avoid contention occurring when optical packet data signals exist in the same time slot, the same number of input terminals as the number of the different wavelengths that are output with a time interval of each optical packet data signal separated by a predetermined time or more are provided. An optical buffer having one output end; and each of the address filters according to an electrical signal output from the photodetector. Optical packet selector, characterized by comprising an address decoder which controls the optical buffer. 2. The number of input terminals to which a plurality of signal lines for transmitting a pre-addressed electric packet signal sequence are input, and the number of input terminals is the same as the number of input terminals, wherein the time length and the number of bits of one packet are constant. In the optical packet switch in which a signal input from one end of the input terminal is output from a predetermined end of the output terminal, one pulse time width corresponds to the one packet bit number of the one packet time length. An optical pulse oscillator having a constant value smaller than the ratio, oscillating an optical pulse of a constant wavelength at a constant cycle, and distributing the oscillated optical pulse into a constant number and outputting the same, and provided for each of the input signal lines. The optical pulse output from the optical pulse oscillator is modulated in accordance with the data portion of the electric packet signal supplied through the input signal line, and one packet time length is set to 1 The optical packet signal is output at a period equal to the one packet time length as an optical packet signal compressed so as to match the product of the number of packet bits and the one pulse time width. An optical packet compressor that outputs a packet address signal, and an optical multiplexer that delays and multiplexes each optical packet signal of an optical packet signal sequence output from the optical packet compressor and outputs the resultant signal. A plurality of optical packet transmitters are installed in parallel, and optical packet signal trains from the same number of optical packet transmitters as the number of the optical pulse oscillators are input, and multiplexed and distributed,
An optical multiplexer / distributor having the same number of input ports as the number of the optical packet transmitters and an output port corresponding to the product of the number of the optical packet transmitters and the time division multiplexing degree is installed. 2. The optical packet selector according to claim 1, further comprising: an input terminal to which an optical packet signal from an output port of the optical multiplexer / demultiplexer is input. An optical packet signal whose time length output from the optical packet selector is equal to the product of the one packet bit number and the one pulse time width is equal to the one packet time length. An optical packet switch, comprising an optical packet decompressor for converting a long electric packet signal.