JPH03117249A - Optical packet switch - Google Patents

Abstract

PURPOSE:To increase number of input signal lines and to realize a large capacity of optical packet switch by using an ultrashort optical pulse with a small pulse width so as to apply ultrahigh speed processing. CONSTITUTION:A packet signal string in which a bit number is L and a time length is T in one packet is fed to an optical packet modulator 101-n via an input signal line 81-n and an optical pulse whose pulse width is (t) and whose period is T/L is fed to the modulator 101-n from an ultrashort optical pulse oscillator 9. Then the pulse is outputted to an input optical highway 111-n as a signal with a bit number of L and a period of T/n, each signal is retarded by an optical multiplexing distributer 12, the signal is subject to time division multiplex and the resulting signal is distributed to n-sets of output optical highways 131-n. An optical address filter 141-n supplies only a coincident signal from packet signals on the relevant highway 13 to a succeeding stage of optical buffer 151-n, the signal is converted into an electric signal whose time length is T via an optical packet demodulator 161-n and outputted to an output signal line 171-n.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical packet switch that is high-speed, large-capacity, non-blocking, and has excellent expandability.

"Prior Art" The configuration of a conventional packet switch using electrical signals that was proposed before the present invention is shown in FIG. 10 (Il, 5U
ZUKI, Il, NAGANO, T, 5UZUK
I, T, TAKEUCIII and S.

11fASAKI, “0output-burrer 5
w1tch Architecture ror As
synchronous Transfer Mode,
"ICC' 89.4.1. June 1989
). The principle of operation will be explained below with reference to FIG.

First, nine input signal lines 1,,1,...1
When a packet signal sequence in which the number of bits in one packet is T and the time length of l packet is T is supplied to each of It is synchronously multiplexed onto the time division highway 3 as a T/n signal. This time division filter circuit 3 is connected to address filter circuits 41.4. . . 4n are constantly monitored by each output signal line 51+ 5, .
... Only packets matching the address corresponding to 5n are allowed to pass. And address filter circuit 4.
．． 4.・・・・・・Packets passing through each of 4n are stored in buffer memory (FIFO memory) 6,, 6,...
...Supplied to 6n. Buffer memory 61, 6 .・・・
...6n each has a corresponding address filter circuit 4.
．． 4. ...Accumulates the signals supplied from 4n,
This is output as a packet of time length T on the signal line 5. .

5, ... Output to 5n. Here, the buffer memories 6, . 6. . . . When packets exceeding the capacity reach each of 6n, those packets are discarded.

"Problem to be Solved by the Invention" By the way, the conventional packet switch mentioned above is called an output buffer type packet switch, and has a simple configuration, no internal blocking, and only requires adding input/output sections on both sides. It has the advantage of being expandable and having fewer ripple effects from failures, but the signal speed on the time-division highway 3 is higher than the time-division multiplexing circuit 2, address filter circuit 4. ．． Since it is limited by the operating speed of 4° . . . 4n, there is a drawback that a sufficient capacity ff1 (input/output signal line 'Rn) cannot be obtained. For example, if the maximum signal speed on time-division highway 3 is 1.2 Gb/S and the signal speed on the input/output signal line is 600 Mb/S, only two input/output signal lines can be accommodated, and in this case, 150 Mb/s.
The limit is to switch the 8 channels of video exchange for 2000/s into 2 ways.

Therefore, in order to expand the throughput, the signals on each input signal line 11+1,...In are converted into low-speed parallel signals by serial/parallel conversion, and multiplexed in parallel on multiple time-sharing highways. However, in this case, the time division multiplexing circuit 2 and the address filter circuit 4.
．． 4. . . . As the number of 4n increases, the configuration becomes more complicated, resulting in a problem that the advantages of this switch are lost.

The present invention was made in view of the above-mentioned circumstances, and an object of the present invention is to provide an ultra-high-speed, large-capacity optical packet switch by applying optical signal processing technology to a conventional output buffer type packet switch.

"Means for Solving the Problems" The optical packet switch of the present invention includes a plurality of input signal lines for transmitting a packet signal sequence in which the number of bits in one packet is L and the time length of one packet is T. In the optical packet switch, the time width of one pulse is t (t<<T/
L) an optical pulse oscillator that outputs the optical pulse at a constant period and distributes the output to a plurality of outputs; and an optical pulse oscillator that is provided for each of the human power signal lines and output from the optical pulse oscillator. The pulse is modulated according to the packet signal supplied via the input signal line, and the time length Lt is 18.
an optical packet modulator that outputs a compressed optical packet signal every period T; a delay is given to each optical packet signal of the previous packet signal sequence output from the optical packet modulator, and time division multiplexing is performed; An optical multiplexer/distributor that distributes the multi-m signal into a plurality of signals and outputs the multi-m signal;
An optical address filter that detects the address assigned to the optical packet signal output from the distributor, compares the detected address with the fixed address assigned to itself, and passes the optical packet signal only if they match. and the time interval of optical packet signals provided for each of the optical address filters and output from the optical address filters is T.
and an optical packet demodulator provided for each of the optical buffers and converting an optical packet signal having a time length Lt outputted from the optical buffer into a packet signal having a time length T. It is characterized by

"Operation" This invention realizes the main functions of a packet switch, such as packet signal modulation, multimeter multiplication, address identification, and buffer 1 ring, by optical signal processing technology using ultrashort optical pulses. By performing ultra-high-speed processing using ultra-short optical pulses with a small width t, the number of input signal lines n=T/
Lt can be made large. For example, if the electrical treatment time is Ins and the ultrashort optical pulse width is 10 ps,
The signal speed is two orders of magnitude faster than that of conventional packet switches using electrical signals, and the switch capacity is also increased by two orders of magnitude.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to the drawings.

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

In this figure, %81+81...80 are input signal lines, and slow electrical signals are supplied to each of these lines. 9 is an ultrashort optical pulse oscillator, to,,t
o, . . . Ion are each optical packet modulators, 11
,．． 11. . . . lln is a human power optical highway, 12 is an optical multimeter/distributor, 13. ．． 13.・・・・・・
13n is each output optical highway, 141.14 *...
...14n are optical address filters, 15. ．． 1
5. . . . 15n are optical buffers, 16. ．． 1
6. ...16n are optical packet demodulators, 17
1+17, . . . 17n are output signal lines, respectively. The operation of this first embodiment will be sequentially explained below based on FIG.

First, through the input signal lines 8, 8, . . . 8n, respectively! When the number of packet bits is L1, the RJI packet signal string of length T is optically packet modulated t4H1o, , 10.
. . . is supplied to each lOn, and the pulse width t1 period T/L (t4CT/
When the optical pulse of L) is opened, the packet modulator 10. ．． 1. O
, . . lon are supplied to each of the optical packet modulators 10 . .

As shown in FIG. 2, each Ion modulates a light pulse according to a packet signal train using a modulator 19 using an electro-optic effect, and further modulates the modulated light pulse into the first bit of the packet. The delay time (T/
When the final bit of the packet arrives, the gate pulse supplied to the lx2 switch 22 outputs the signal from the same 1x2 switch 22. do. In this case, by supplying the gate pulse to the lx2 switch 22 at a period T, the packet signal is converted into a signal in which the number of bits in one packet is L1 and the time length is T/n (=Lt) every period T to the input optical highway 11. ,．． 11.・・・・・・
Output to lln. Here, in order to be able to separate the address part and data part of the compressed optical pulse packet in the subsequent processing using an electro-optic switch, etc., a time period of S is preliminarily added to the rear part of the address signal as shown in FIG. We will provide a dummy bit for this.

Next, as shown in FIG. 4, the optical multiplexer/distributor 12 connects the input optical highway 11. ．． 11.・・・・・・For each signal on lln, i・(T/n 15) (i= 1.2.-, n
) after giving a delay of more than
．． ．． 13. ...Distribute to 13n. At this time, an interval of S time is provided between the multiplexed packets so that each packet can be separated by an electro-optical switch or the like in subsequent processing.

Next, the optical address filter l 41+ 14 ,...
. . . 14n is the corresponding output optical highway 13
,,13,...13n, the address of the packet signal on the same output optical highway 13. ,131...
Only when the address matches the address of the optical buffer 15.13n, this packet signal is transferred to the next stage optical buffer 15. ．． 15.・・・・・・１
5n.

Optical address filter 14,, 141...14n
As shown in FIG. 5, first, only the address part of the packet signal is separated by the splitter 24 and the lxl optical switch 25, and this is separated from each output optical highway 13. ,13.・
...13n is supplied to the decoder 26 having a unique delay line pattern, and only when the address of the packet matches the address of the output optical highway 131+13, ...13n, the maximum autocorrelation output is Generates a peak superimposed pulse (this decoder uses optical
This is a decoder used for CDMA ncLwork.

References: Paul R, Prucnal, etc.”
5pread Spcctrum Fiber-opt
ic Local Area Network Usi
ngOptical I'roccssing', Jo
urnal or Lightwavc Techno
logic, vol, LT-4, No, 5. Ma
y 1986). This maximum pulse is converted into a light/T1 air converter (
0/E converter) 27 into an electrical address detection signal, this address detection signal controls the lxl optical switch 28, and the optical packet signal is sent to the next stage optical buffer 15. .

! 5. ......Supplied to 15n. At the same time, the address detection signal is also transmitted to the next stage optical buffers 15, 151, .
...Supply to 15n.

Next, the optical buffer 15. ．． 15. ......15n each has an optical address filter l 4 ,, l 4 , .
...14n, the time interval of the optical packet signal is separated by more than 'r, and the next stage optical packet demodulation 2a161.1
6-...Output to 16n. Each optical buffer y15
．． ,15. ...15n is k lx as shown in Fig. 6 (however, Fig. 6 shows the case where = 4)
2-light switch 29. .

29 ,...=29 k and 1x2 optical switch 2
91+29.

・・・・・・In 29, delay time (T/
n+S) delay line 30+, 30t...-3
0, IX2 optical switch 291+ 29,...
...29, the delay time 1-T (i=1
,2. . . .+n). ．． 31.・・・
...31, and the delay line 31. ．． 31,...
a coupler 32 that couples the respective outputs to the lK2 optical switch 29 . ．． 29. . . . 29 includes a counter 33 and a decoder 34 for controlling each operation.

Optical buffer 15. ．． 15. ...15n is each
The corresponding optical address filters l 4 ,, l 4 ,
. . . The optical packet signals supplied from 14n are sequentially transferred to 1x2 optical switches 29 , 29 , . . . 2
9k, while the corresponding optical address filter 1
The counter 33 counts the address detection signals supplied from 4, l4, . . . 14n,
If the count value is p (-1 for 0≦p≦), the decoder 34 selects the p+1st IX2 optical switch 29p.
++ and supplies this packet to the coupler 32 via the delay line (P+1)·T. The count value of the counter 33 is counted down by one every (T+T/n) time. If the count value is greater than or equal to the count value in the packet queue, the packet passes through the 1.times.2 switch 29k as an overflow and is discarded. This optical buffer 151+15t...15n allows packet time intervals to be separated by T or more. Further, the countdown period of the counter 33 is the time division multiplexing period T.
, the packet discard probability is the same for all multiplexing positions.

Finally, optical packet recovery: iy4'? 316. ．． 16.
.....16n each has a corresponding optical buffer 15+
+15*...Time length T/ supplied from 15n
Input signal line 11+ corresponding to packet n (=Lt)
Output signal line 171 that converts into an electrical signal of the same time length T as the packet supplied to 1, . . . 1n and corresponds to it.
+ 17 , ... Output to 17n. In this case, if there is no element for converting ultrashort optical pulses directly into electricity, the signal is branched into L systems as shown in Figure 7, and each optical pulse with period T is converted into 1 bit ( time t
) and superimpose the peak pulses by shifting and superimposing the peak pulses by the optical/electrical conversion element 35. ．． 35=・・・351. This detection result is stored in the latch circuit 36, and read out every period T as a packet signal string of time length T.

Through the above operations, the pilot packet switch transfers the packets on the manual signal lines 8, 8, . . . 8n to the output signal lines 17, 17, . . . corresponding to each address.
...17n, self-routing connection can be made as a packet of the same format. With the pilot packet switch, the signal speed can be increased to the limit of ultra-short optical pulse width, and the input signal lines 8 , , 8 ,...!・n of 8n =
Since T/Lt can be made large, a large-capacity first packet switch can be realized.

Next, a second embodiment of the present invention is an improvement on the basic configuration of the first embodiment described above, and the wavelength λ.

The ultrashort optical pulses λ and λ are modulated by the address part and data part of the input packet signal, respectively, so that the two parts can be easily separated. That is, in FIG. 1, an optical pulse oscillator 9 that outputs ultrashort optical pulses with wavelengths λ1 and λ is used, and these are modulated by the address part and data part of the input packet signal, respectively, as shown in FIG. A signal such as input optical highway l11. Ill...Output to lln. In this case, addresses and data do not need to be temporally separated within the l bucket.

In this second embodiment, since address separation in the optical address filter can be realized by a wavelength filter (see Figure 9), dummy bits for S time for time separation are provided between the address and data as in the first embodiment. (See Figure 3) There is no need to provide one. This allows ultra-high signal speeds,
Can be used more effectively. Note that the other configurations are the same as those of the first embodiment, and will therefore be omitted.

Note that in the above embodiment, the number of distributions of the optical strip m/distributor 12 and the number of input signal lines are made the same, but the number of distributions of the optical multiplexer/distributor 12 does not depend on the number of input signal lines. do not have.

"Effects of the Invention" As explained above, the optical packet switch of the present invention uses a large number of input signal lines n=T/Lt to perform ultra-high-speed processing using ultra-short optical pulses with a small pulse width. Therefore, a large-capacity optical packet switch can be realized. For example, if the length of one pit of an output buffer type packet switch using a conventional electric signal is Ins,
If the width of the ultrashort optical pulse is 10 ps, the capacity of the switch can be increased by two orders of magnitude.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an optical packet switch according to the first embodiment of the invention, FIG. 2 is a block diagram showing the configuration of an optical packet modulator according to the first embodiment, and FIG. A diagram showing the format of an optical packet signal modulated by optical packet modulation 2K in the first embodiment, FIG. 4 is a block diagram showing the configuration of the light strip m/distributor in the first embodiment, and FIG. FIG. 6 is a block diagram showing the configuration of an optical buffer in the first embodiment; FIG. 7 is a block diagram showing the configuration of an optical packet demodulator in the first embodiment. FIG. 8 is a block diagram showing the format of an optical packet signal according to the second embodiment of the present invention. FIG. 9 is a block diagram showing the configuration of the optical address filter according to the second embodiment. FIG. 1 is a block diagram showing the configuration of a conventional output buffer type packet switch. 8, to 8n: input signal line, 9; ultra-short optical pulse oscillator (first pulse oscillator), 10,
~10n: Previous packet changer yJJ device, 11, ~I In
: Input optical highway, 12 Two-optical multiplexer/distributor, 13, ~13n: Output optical highway, 14, ~14n: Optical address filter, 15+~15n
: Optical buffer, 16, ~16n : Optical packet demodulator, 17, ~17n
: Output signal output amount applicant Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] (a) In an optical packet switch equipped with a plurality of input signal lines for transmitting a packet signal sequence in which the number of bits of one packet is L and the time length of one packet is T, (b ) an optical pulse oscillator that outputs an optical pulse with a one-pulse time width of t (t≪T/L) at a constant cycle, and divides the output into a plurality of outputs; (c) each of the input signal lines; modulates the optical pulse output from the optical pulse oscillator according to the packet signal supplied via the input signal line;
an optical packet modulator that outputs a compressed optical packet signal with a packet time length Lt every period T; (d) giving a delay to each optical packet signal of the optical packet signal train output from the optical packet modulator; (e) an optical multiplexer/distributor that performs time division multiplexing and further distributes and outputs the multiplexed signal into a plurality of signals; An optical address filter that detects an address given to an optical packet signal output from a device, compares the detected address with a fixed address given to itself, and passes the optical packet signal only if they match. , (f) provided for each of the optical address filters,
an optical buffer that separates the time interval of optical packet signals output from the optical address filter by T or more; and (g) an optical packet signal provided for each of the optical buffers and output from the optical buffer with a time length of Lt. an optical packet demodulator for converting the signal into a packet signal having a time length T.