JPH06261072A - Optical packet selector and optical packet switch - Google Patents

Abstract

PURPOSE:To attain large capacity and high speed of an optical packet switch by applying optical signal processing to a major function of the packet switch through the use of an ultrashort optical pulse. CONSTITUTION:High speed packet data and an optical address signal generated by an optical packet compressor 10 are subject to time division multiplex by an optical multiplexer 11 and the result is inputted to an optical synthesis branching device 13, where wavelength multiplexing is executed and the data are distributed into mn-lines of outputs and inputted to an optical packet selector 14. Then optical packet signals subject to wavelength multiplexing and time division are selected altogether for buffering and the result is inputted to an optical packet expander 15, in which an optical packet signal whose time length is Lt is converted into an electric packet signal whose time length is T. High speed processing is executed by using an ultrashort optical pulse having a very small pulse width in this way to increase the degree of time division multiplex and wavelength multiplexing is applied further thereby realizing a large capacity optical packet of Tbit/s.

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 high speed, large capacity and excellent expandability, and an optical packet switch using the same.

[0002]

2. Description of the Related Art The configuration of a conventional packet switch using electric signals 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, see).

In FIG. 9, reference numeral 91 is an input signal line, 92 is a time division multiplex 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.

The operating principle will be described below 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 synchronously multiplexes the time-division highway 93 as a signal having a packet length of T / n. The time-division highway 93 is constantly monitored by the address filter circuit 94, and only the packet matching the address corresponding to each output signal line 96 is passed. Then, the packet that has passed through the address filter circuit 94 is supplied to the buffer memory (FIFO memory) 95. Each of the buffer memories 95 accumulates the signal supplied from the corresponding address filter circuit 94, and outputs this to the output signal line 96 as a packet of time length T. Here, when a packet having the capacity or more 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 expanded by adding an input / output unit to both sides, and a further fault occurs. However, since the signal speed on the time division highway is limited by the operation speed of the time division multiplexing circuit or the address filter circuit, there is a problem that sufficient capacity cannot be obtained.

For example, if the signal speed on the time-division highway is 1.2 Gbit / s at the maximum and the signal speed on the input / output signal line is 600 Mbit / s, only two input / output signal lines can be accommodated. The limit is to switch 8 channels of 150 Mbit / s moving image exchange to two routes.
Therefore, in order to increase the throughput, a method of converting signals on each input signal line into parallel signals of low speed by serial / parallel conversion and multiplexing them in parallel to a plurality of time division highways is conceivable. Since the number of time division multiplexing circuits and address filter circuits increases and the configuration becomes complicated, there is a problem that the above advantages of the present switch are impaired.

Therefore, as a means for solving the above-mentioned problems, for example, an optical packet switch using an optical signal has been proposed, as described in Japanese Patent Application No. 1-255043 (Reference 2). This aims at expanding the switch capacity as compared with the conventional packet switch using an electric signal by utilizing the high speed / broad band property of light and the wide band property of an optical fiber.

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

The operation will be described below with reference to FIG.
The n input signal lines 81 are input to the n optical packet modulators 83. In each optical packet modulator 83, the optical pulse distributed from the ultrashort optical pulse oscillator 82 is modulated by the electric packet signal transmitted through the input signal line 81 and input to the optical packet modulator 83, and then the high speed optical packet is generated. Convert to signal.

This high-speed optical packet signal is input to the optical multiplexer / distributor 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 address of the outgoing line. In the optical buffer 86,
The time interval from the output of the input optical packet signal to the output of the next optical packet signal is separated by T or more and output to the optical packet demodulator 87. The optical packet signal input to the optical packet demodulator 87 is converted into an electric signal having the same time length T as that of the packet supplied to the input signal line 81, and then output.

The optical address filter 85 shown in FIG. 8 does not have a function of selecting an optical packet for a wavelength-multiplexed signal.

[0012]

However, in the above-mentioned conventional optical packet switch, in reality, there are difficult problems such as generation of ultrashort optical pulses, control speed by electric signals, synchronization technology, etc. 2 of the electric packet signal
It is thought that the capacity will increase by only about one digit.
There is a problem that it is not possible to cope with high-speed signal processing with a large capacity of t / s or more.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a large capacity and high speed optical packet switch having a signal processing speed of Tbit / s class. is there.

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

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

[0016]

In order to achieve the above object, the optical packet selector of the means (1) of the present invention has a plurality of different wavelengths, each of which is assigned a different wavelength address. A wavelength having an input end to which an optical packet signal wavelength-multiplexed with pulsed light is input, and demultiplexing the input optical packet signal into two components, an optical packet data signal and an optical packet address signal, and outputting them. A demultiplexer and an address wavelength demultiplexer that demultiplexes and outputs the same number of optical packet address signal sequences output from the wavelength demultiplexer as the number of different wavelengths included in the optical packet signal, The optical packet address signal output from the address wavelength demultiplexer is converted into an electric signal by the same number of photodetectors as the number of different wavelengths, and the optical packet data signal sequence output from the wavelength demultiplexer is the Difference A wavelength demultiplexer for data having an output end that demultiplexes the same number as the number of wavelengths to be output, and a fixed address is previously given to the address filter itself, and the light output from the wavelength demultiplexer for data is provided. The optical packet is detected only when the packet data signal is detected and the address of the address signal given to the detected optical packet data signal before being demultiplexed by the wavelength demultiplexer matches the fixed address. As many address filters as the number of the different wavelengths for passing the data signal and each of the address filters are provided so as to avoid the conflict that occurs when the optical packet data signals output from the respective address filters exist in the same time slot. The optical packet data signal has the same number of input terminals and one output terminal as the number of different wavelengths that are output with a certain time interval or more apart between them. 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, the time length and the number of bits of one packet are constant, and a plurality of signal lines for transmitting an electric packet signal sequence to which an address is given in advance are input. In an optical packet switch having a terminal and the same number of output terminals as the number of the input terminals, and a signal input from one end of the input terminal is output from a predetermined one end of the output terminal, one pulse time width is equal to the one packet time. An optical pulse oscillator that is a constant value smaller than the ratio of the length to the number of 1 packet bit, oscillates an optical pulse of a constant wavelength at a constant cycle, and distributes the oscillated optical pulse into a constant number and outputs the 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 via the input signal line, An optical packet signal compressed so that the packet time length matches the product of the one packet bit number and the one pulse time width is output at a cycle equal to the one packet time length, and the address portion of the electrical packet signal is output. An optical packet compressor for laser-modulating according to the above, and outputting as an optical packet address signal, and an optical multiplex for delaying each optical packet signal of an optical packet signal sequence output from the optical packet compressor for time division multiplexing and outputting. A plurality of optical packet transmitters composed of an optical packet transmitter are installed in parallel, the same number of optical packet signal trains from the optical packet transmitters as the number of the optical pulse oscillators are input, and multiplexing and distributing are performed. Optical multiplexing / demultiplexing having the same number of input ports as the number of optical packet transmitters and the output port of only the product of the number of the optical packet transmitters and the time division multiplexing The optical packet selector according to claim 1 having an input terminal to which an optical packet signal from the output port of the optical packet transmitter is input, One optical packet signal is installed for each of the output ports, and the 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 installed in the optical packet decompressor for converting into an electric packet signal having a time length equal to the one packet time length.

[0018]

According to the above-mentioned means, in the optical packet switch, the main functions of the packet switch such as packet signal modulation, multiplexing, address identification, and buffering are realized by using the optical signal processing technique using the ultrashort optical pulse. The ultra-short optical pulse has a very small pulse time width, so the time-division multiplex of the optical packet signal can be increased, and the wavelength-division-multiplexing of the optical multiplexer / demultiplexer makes it possible to obtain the input signal. Since the number of lines can be increased by the number of wavelength multiplexing of the related art, it is possible to obtain an optical packet switch having a switch capacity larger than that of the conventional optical packet switch. For example, if the electrical processing time is 1 ns, the width of the ultra-short optical pulse is 10 ps, and the wavelength multiplexing number is 10, then the signal speed of the packet switch using conventional electric signals is increased by three digits, and the switch capacity is expanded to three digits. However, a signal processing speed of Tbit / s level can be obtained.

[0019]

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

FIG. 1 is a block diagram showing the configuration of an embodiment of the optical packet selector of the present invention, in which 1 is a wavelength demultiplexer,
2 is a wavelength demultiplexer for address, 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 for an optical data signal A wavelength demultiplexer (data wavelength demultiplexer), 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 demultiplexes 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 for different wavelengths, detected by 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, the output buffer type optical switch can collectively select and buffer the wavelength-multiplexed and time-divided 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 the optical packet selector of the present invention, 8-i-j (where j is a natural number and j = 1, 1).
2, ... N) are input signal lines, respectively, to which slow electric signals are supplied. Reference numeral 9-i is an ultrashort optical pulse oscillator, 10-i-j is an optical packet compressor, 11-i is an optical multiplexer, and 12-i is an optical packet transmitter.
The ultrashort optical pulse oscillators 9-i of the optical packet transmitters oscillate different wavelengths λi, respectively. Reference numeral 13 is an optical multiplexer / demultiplexer. 14-h (where h is a natural number and h =
1, 2, ..., MN) are optical packet selectors. 15
-h is an optical packet decompressor. In the following description, FIG.
The operation of the optical switch according to the present embodiment will be sequentially described with reference to FIG.

FIG. 3 is a block diagram showing the structure of the optical packet compressor 10-i-j shown in FIG. 2. 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.

A pre-addressed electrical packet signal input to each optical packet compressor 10-i-j via each input signal line 8-i-j is converted into an address signal (time signal) by a data / address divider 16. It is divided into a length T ₁ ) and a data signal (bit number L, time length T ₂ ). After that, from the ultrashort optical pulse oscillator 9-i, the pulse width t and the period T / L (however,
T = T ₁ + T ₂ , t <T / L), and when the optical pulse of wavelength λi is supplied to the optical packet compressor 10-i-j, the optical packet compressor 10-i-j As shown in FIG. 3, the light intensity modulator 17 modulates the light pulse according to the data signal.

Further, the modulated optical pulse is passed through a circuit consisting of a 1 × 2 optical branching device 18, an optical fiber delay line 19 and a 2 × 1 optical coupler 20 for k stages, and then an optical gate switch 21 is used. By removing the extra pulse, a high-speed optical packet consisting of 2 ^k pulses is generated (Japanese Patent Application No.
-See the ultrashort optical pulse modulator circuit of 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, and in FIG. a) is the pulsed light output from the light intensity modulator 17, (4-b) is the pulsed light output from the first stage 2 × 1 optical coupler 20, and (4-c) is k.
The pulsed light output from the second 2 × 1 optical coupler 20 is
(4-d) is 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 the optical address signal are combined by the optical coupler 23 and output as the output of the optical packet compressor 10-i-j.

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

In the optical packet selector 14-h shown in FIG. 1, the optical packet selector 14-h demultiplexes the optical packet signal into data and address by the wavelength demultiplexer 1 described above, and the address is divided by the address wavelength. Wavelengths 2 are demultiplexed into addresses for different wavelengths, and photodetectors 3-1 to 3-3 are respectively provided.
Detected by -m and input to the address decoder 7. Then, 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 the 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, where 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 of time interval T or more. Optical packet selector 14-h
The optical packet signal output from the optical packet expander 15-
Input to h.

FIG. 6 is a block diagram showing the configuration of the optical packet expander 15-h. 27 is a 1 × 2 optical switch, 28 is an optical fiber delay line, and 29 is a 2 × 1 optical coupler (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 a side of the 1 × 2 optical switch 27 with the optical fiber delay line 28. This is the output switch port. The optical packet signal input to the optical packet decompressor 15-h is transmitted through a circuit including 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, it is converted into an electric signal by the photodetector 30 to convert the optical packet signal of the time length Lt into the electric packet signal of the time length T (for details, refer to Japanese Patent Application No. 4-41106 “Optical Pulse”). Interval extender ").

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, and (7-a) is to the optical packet decompressor 15-h. The input light, (7-b) is the control signal for the first stage 1 × 2 optical switch 27, (7-c) is the output light at the switch port # 1, and (7-d) is the switch port # 2. (7-e) is the output light from the coupler 29 at the first stage, (7-f) is the control signal to the 1 × 2 optical switch 27 at the second stage, and (7-g) is The output light from the coupler 29 in the second stage and (7-h) show the output light from the coupler 29 in the kth stage with respect to the horizontal time axis.

From the above description of the operation, the optical packet switch of this embodiment shown in FIG. 4 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 nm switching function is accurately performed.

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

That is, the pulse time width t of the ultrashort optical pulse
Is very small, the time division multiplexing degree of the optical packet signal can be made large, and the wavelength division multiplexing is further performed by the optical multiplexer / demultiplexer 13, so that the input signal line is multiplied by the conventional wavelength multiplexing number. Therefore, it is possible to obtain an optical packet switch having a larger switch capacity than the conventional optical packet switch.

For example, the switch throughput (capacity) of the optical packet switch of this embodiment is a laser diode of 1.55 μm band for an optical data signal (ultra-short optical pulse) and a laser diode of 1.3 μm band for an optical address signal. If the practical optical pulse width obtained from the laser diode is 10 ps, the number of wavelengths can be estimated to be about 10 from the band of the optical device (optical amplifier, switch, etc.), and the signal processing capability of several Tbit / s. Engrave.

Although the present invention has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention. Absent.

[0039]

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

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

[Brief description of 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 the configuration of an optical packet switch according to an embodiment of the present invention,

FIG. 3 is a block diagram showing the 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 the configuration of an optical packet decompressor,

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

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 ... Address wavelength demultiplexer, 3-i ...
Photodetector, 4 ... Wavelength demultiplexer for data, 5-i ... Address filter, 6,86 ... Optical buffer, 7 ... Address decoder, 8-i-j ... Input signal line, 9-i ... Ultra-short optical pulse Oscillator, 10-i-j ... 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 divider, 17 ... Optical intensity modulator, 18 ... 1 × 2 optical branching device, 19 ... Optical fiber delay line, 20 ... 2 × 1 optical coupler, 21 ... Optical 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 multiplexer / demultiplexer, 85 ... Optical address filter, 87 ... Optical packet demodulator.

Claims (2)

[Claims] 1. An optical packet signal which has an input end to which an optical packet signal wavelength-multiplexed with a plurality of pulsed lights having different wavelengths and to which addresses of different wavelengths are given respectively, are input. A wavelength demultiplexer for demultiplexing into two components, an optical packet data signal and an optical packet address signal, and a train of optical packet address signals output from the wavelength demultiplexer are included in the optical packet signal. An address wavelength demultiplexer that demultiplexes and outputs the same number as the number of different wavelengths, and the same number as the number of different wavelengths that converts the optical packet address signal output from the address wavelength demultiplexer into an electrical signal. And a data wavelength demultiplexer having an output end that demultiplexes the optical packet data signal sequence output from the wavelength demultiplexer by the same number as the number of different wavelengths and outputs the demultiplexed signal. The fixed address is given to the optical filter itself, and 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. To the address signals of the same number as the number of the different wavelengths that pass the optical packet data signal only when the address of the address signal assigned to the address filter is output from each of the address filters. And 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 being separated by a certain time or more so as to avoid a conflict that occurs when the optical packet data signals are present in the same time slot. An optical buffer having one output end, and each of the address filters according to an electric signal output from the photodetector Optical packet selector, characterized by comprising an address decoder which controls the optical buffer. 2. An input terminal to which a plurality of signal lines for transmitting an electric packet signal sequence to which an address is given in advance is input and the same number as the number of the input terminals, in which 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 that oscillates an optical pulse having a constant wavelength that is a constant value smaller than the ratio in a constant cycle, and that outputs the oscillated optical pulse by dividing the oscillated optical pulse into a fixed number, and that is provided for each of the input signal lines. The optical pulse output from the optical pulse oscillator is modulated according to the data portion of the electric packet signal supplied through the input signal line, and one packet time length is 1 An optical packet signal compressed to match the product of the number of packet bits and the one pulse time width is output at a period equal to the one packet time length, and laser modulation is performed in accordance with the address portion of the electrical packet signal to generate an optical signal. An optical packet compressor for outputting as a packet address signal, and an optical multiplexer for delaying each optical packet signal of the optical packet signal sequence output from the optical packet compressor for time division multiplexing and outputting. A plurality of optical packet transmitters are installed in parallel, optical packet signal trains from the same number of optical packet transmitters as the number of the optical pulse oscillators are input, and multiplexing and distributing are performed,
An optical multiplexer / distributor having the same number of input ports as the number of the optical packet transmitters and the output port having only the product of the number of the optical packet transmitters and the time division multiplicity is installed. 2. The optical packet selector according to claim 1 having an input terminal to which an optical packet signal from each of the output ports of the optical multiplexer / divider is provided, the number being equal to the number of output ports of the optical multiplexer / distributor. The optical packet signals output from the optical packet selector have a time length equal to the product of the 1 packet bit number and the 1 pulse time width. An optical packet switch comprising an optical packet expander for converting a long electric packet signal.