EP0282227A1 - Processeur de commutation de signal - Google Patents

Processeur de commutation de signal Download PDF

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Publication number
EP0282227A1
EP0282227A1 EP88301841A EP88301841A EP0282227A1 EP 0282227 A1 EP0282227 A1 EP 0282227A1 EP 88301841 A EP88301841 A EP 88301841A EP 88301841 A EP88301841 A EP 88301841A EP 0282227 A1 EP0282227 A1 EP 0282227A1
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EP
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Prior art keywords
signals
input
output
processor
signal
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EP88301841A
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German (de)
English (en)
Inventor
John Edwin Midwinter
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British Telecommunications PLC
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British Telecommunications PLC
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Publication of EP0282227A1 publication Critical patent/EP0282227A1/fr
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06E—OPTICAL COMPUTING DEVICES; COMPUTING DEVICES USING OTHER RADIATIONS WITH SIMILAR PROPERTIES
    • G06E3/00—Devices not provided for in group G06E1/00, e.g. for processing analogue or hybrid data
    • G06E3/006—Interconnection networks, e.g. for shuffling

Definitions

  • the invention relates to a signal switching processor.
  • an optical signal switching network in which optical data input signals from a number of input ports are passed through a series of switching units and an optical redistribution network so as to convey each optical signal to a respective output port.
  • the network described can be reset very easily since the switching units are each formed from a number of self-setting exchange-bypass modules.
  • Each module has two input ports and two output ports and can exist in one of two states thus linking each input port with a selected one of the output ports.
  • the state of each module is set within the module during a reset operation by supplying as data input signals the addresses of the desired output ports for subsequent data from the corresponding input port.
  • the redistribution optics together with the exchange-bypass modules are arranged so as to perform a perfect-shuffle algorithm on the addresses supplied during a reset operation.
  • Each exchange-bypass module comprises a pair of detectors for detecting respective input beams, a logic system, and a pair of output beam modulators which are controlled by signals from the logic system in accordance with the logic state of the module. To implement these modules, it is then necessary to supply auxiliary read beams to each of the modulators. The source of these read beams is not shown in the paper mentioned above and indeed in practice it would be very difficult to implement the arrangement shown in the paper.
  • one solution might be to incorporate within the modules some means for generating the required modulated beams. However, it would then be necessary to mount the arrays on a large heat sink and this would then lead to further complex problems of fabrication.
  • a signal switching processor has a plurality of input and output ports, and a number n of signal switching units arranged in series between the input and output ports and coupled together so as to generate at each output port a data output signal corresponding to a data input signal supplied to a respective input port, the switching units being mounted in an array of rows, being coupled together by coupling means, and being responsive to received data signals to modulate respective read signals incident on the switching units, each of the leading n-1 switching units causing the modulated read signals to be reflected towards the coupling means which couples the signals with the next row in the array of switching units.
  • the invention also enables the source of the read signals to be positioned at a location remote from the switching units and in one example, the read signals may be supplied to the switching units from substantially the same position as the data input signals.
  • each switching unit comprises a number of electro-absorption modulators one for each processor input port, the modulators being adapted to reflect an incident read beam and to modulate the read beam in accordance with data signals supplied to the switching unit.
  • Typical EAMs have a thickness of about 1 ⁇ m which in general is not sufficiently thick for there to be a good extinction ratio. However, by operating the modulator in a reflection mode, the incident read signal passes twice through the modulator thus doubling the absorbtion and leading to a much higher extinction ratio.
  • each switching unit may comprise a number of photodetectors, one for each input port, a number of optical signal modulators, one for each output port, and logic means to which signals from the photodetectors are fed and which passes the signals in accordance with its logical state to respective optical signal modulators which modulate respective read beams in accordance with the signals supplied.
  • the photodetectors comprises electro-absorbtion modulators.
  • both the photodetectors and modulators comprise EAMs, this leads to a particularly simple fabrication of the switching units.
  • each switching unit will comprise at least one exchange-bypass module having first and second input ports and first and second output ports, the module status being selectable such that in a first state the first input and output ports and the second input and output ports are coupled together, and in a second state the first input port is connected to the second output port and the second input port is connected to the first output port.
  • the coupling means comprises a system which in conjunction with the switching units enables a perfect shuffle algorithm to be performed during a reset operation.
  • the coupling means may comprise an optical redistribution network through which the modulated read signals are passed prior to impinging on the next succeeding row in the array of switching units.
  • the read signals for each switching unit are generated by a respective laser
  • the processor further comprising splitting means for splitting the beams generated by each laser into a number of subsidiary beams, one for each processor input port.
  • each switching unit will further include clock means for controlling operation of the switching unit, the clock means being controlled by clock signals supplied to the array of switching units.
  • the clock signals may also be supplied from substantially the same position as the read signals and it is particularly convenient in the case where the clock and read signals comprise optical signals, if the splitting means is adapted to generate from each laser beam one or more additional subsidiary beams to constitute clock signals.
  • the signal switching assembly or processor to be described includes a pipeline sort matrix formed from a number of groups of exchange/bypass modules (EBMs).
  • EBMs exchange/bypass modules
  • An example of the logical construction of an EBM is shown in Figure 1 and comprises four AND gates 1-4 whose outputs are coupled to respective inputs of a pair of OR gates 5, 6.
  • the EBM has two input ports A, B connected to the AND gates 1, 2; 3,4 respectively and two output ports D, E connected to the OR gates 5, 6 respectively.
  • the output ports of the AND gates 1, 3 are connected to the input ports of the OR gate 5 while the output ports of the AND gates 2, 4 are connected to the input ports of the OR gate 6.
  • the status of the EBM is set by a control signal C fed to the AND gates 1, 4 and its logical complement C fed to the AND gates 2,3.
  • the EBM is set in its bypass state when the control signal C is logical 1 resulting in a signal on the input port A being passed to the output port D and a signal on the input port B being passed to the output port E.
  • the control signal C is logical zero
  • the EBM is in its exchange state in which the signal on input port A is coupled with the output port E and the signal on input port B is coupled with output port D.
  • Figure 2 illustrates a generalised sort processor having N input ports and N output ports.
  • the input ports are connected in pairs to respective EBMs of a first group 7 whose output ports are connected to a redistribution network 8.
  • the redistribution network has a fixed pattern and couples each input line with a respective output line.
  • this generalised sort processor comprises a number of pairs of EBM groups and redistribution networks together with a final group of EBMs 9 connected to the output ports of the processor.
  • the redistribution networks should be arranged such that the matrix performs a perfect shuffle algorithm. This is particularly suitable for optical signal implementation since each redistribution network has an identical form and so can be fabricated by a common network.
  • logical EBM a module that includes the logic to establish whether it should self set to the exchange or bypass state according to the address data presented to it through its input ports.
  • the "0" module always bypasses whilst the "+” and “-” modules always route the larger of the two addresses (numbers) to the port marked "h”. They are thus logically identical in structure but are mirror images in function.
  • Figure 5 shows the logical layout for a full 32x32 matrix using the perfect shuffle sort algorithm for its self addressing function.
  • the layout has been deliberately split into five groups of five rows, with each row containing 16 modules.
  • the data lines emerging from each row of 16 EBMs are perfect shuffled before entering the next row.
  • the input data has been sorted into 8 bitonic sequences, with the adjacent pairs of inputs reversed or not according to the address size and spatial position.
  • the addresses have been sorted into 4 bitonic sequences, 2, 1 and finally into a linearly ascending sequence at row 25.
  • each EBM is determined by address data supplied to each input port of the matrix. This address data defines the matrix output port to which subsequent signals are to be switched.
  • the use of logical EBMs is particularly advantageous in this connection since they respond to the relative size of the two addresses arriving at each input port of the respective pair (see Truth Table of Figure 3B). The only action required on the EBM is always to deliver the larger number to the same defined (by position) exit port. Such a logical operation on binary MSB first addresses is trivial, since identical bits always pass directly through. The first pair of bits in the address to differ then define uniquely the larger of the two numbers.
  • Figure 3a illustrates the overall logical circuit for an EBM where I1, I2, O1, O2 are the input ports and output ports respectively; R indicates a reset signal; and P, Q indicate control inputs and outputs for latching the EBM in one of its two states.
  • the reset signal R will be logical 1 and the signals P, Q will define whether the state is bypass, exchange, or not yet set.
  • the reset signal is switched to zero causing Q(n) and P(n) to be zeroed thus implying that the EBM is thereafter not set and preparing the EBM to be set once the reset signal returns to logical 1.
  • Figures 6 to 9 illustrate a practical implementation of a perfect shuffle sort matrix of the type shown in Figure 2.
  • each redistribution network has an identical form and in this example is defined optically by a lens system 11.
  • this shuffle optics relies upon the concept of magnifying an image laterally by a factor of 2, shearing the image into two, and overlaying the two halves to form a shuffled image. It also has some additional advantages not previously achieved since it allows the whole optical system to be folded into a compact sub unit embracing the return data path to the array. It also brings together all the input/output and control channels in a single port 12 located opposite the logic array 10.
  • the logic array 10 is fabricated on a single chip of for example GaInAs/InP with a band gap in the 1300-1500 nm region.
  • the array comprises a number of MQW electro-absorption modulators (EAM), two for each EBM, each of which can be addressed by an externally generated "read" laser beam.
  • EAM MQW electro-absorption modulators
  • FIG. 9 An example of one EBM within the logic array is shown in Figure 9.
  • This comprises a pair of photodetectors 13,14 formed, for example, from electro-absorbtion modulators.
  • the electronic output signals from these photodectors 13, 14 are fed to respective gain and thresholding circuits 15 whose outputs are fed to an EBM logic circuit 16.
  • a photodetector 17 also formed from an electro-absorbtion modulator is responsive to a clock laser beam to provide clock signals to the EBM logic circuit 16.
  • the electronic output signals from the EBM logic circuit 16 are fed to respective EAM drivers 18, 19 which drive respective electro-absorption modulators 20, 21.
  • An external read beam is supplied to each EAM 20, 21 which modulates the beam to generate the required output signal.
  • the optical source of the "read" beam can be located away from the active chip and can thus dissipate its heat elsewhere. This has a secondary, but important advantage, that this enables the beam also to be used for timing and control purposes.
  • the exit beam direction can be derived from the input. This is highly desirable in order to implement the shuffle wiring scheme.
  • EAMs are known to be inherently fast (sub 100 ps switching speed), are readily fabricated and lend themselves to monolithic integration. They are also (optically) non-resonant so that they are relatively insensitive to temperature and wavelength.
  • the input/output system positioned at the port 12 in Figure 6 is illustrated in detail in Figure 7.
  • a composite, layered I/O structure 22 shown in detail in Figure 7A This comprises the output end of an input fibre array 23 composed of a number of optical fibres, one for each input port of the matrix, as a top layer followed by alternate layers of microlenses 24 and reflectors 25, there being one pair of layers 24, 25 corresponding to each row of EBMs, and terminating with the input end 26 of an output fibre array 27.
  • each EBM In order for the EBMs to function, it is necessary to supply three pump laser beams to each EBM. These provide the two "read" beams to the EAMs 20, 21 and the clock beam supplied to the photodetector 17.
  • Each set of three beams is provided in this example by a respective laser the power from which is fanned out into 3 N/2 spots (N is the number of EBMs) on the associated row position on the I/O element 22 to generate three beams to each EBM.
  • These beams are fed via the microlenses 24 associated with the respective EBM row to the logic array 10.
  • Each laser thus provides synchronisation and interrogation for all the EBMs in a single logical row of the pipeline. The laser will be clocked with the appropriate phaseing for that row position. Since all the M(M-1)+1 clock lasers can be colocated in a linear array and will require identical delays between each, it is believed that very accurate clocking should be possible. In addition, the rows enjoy zero clock skew as a result of the
  • interrogation beams from the pump source previously described are injected via the first row of microlenses 24, the interrogation beams impinging onto the logic array at different angles which will be imposed upon them by means of prisms (solid or holographic) located at the I/O element 22.
  • the prisms are indicated by reference numeral 30 ( Figure 6). The reason for this is that it is desirable to spatially separate the optical beams emerging from the two halves (1 to P and P+1 to N) of the array in order to operate the shuffle optical system with minimum power loss.
  • the two read beams are reflected from the respective EAMs 20, 21 after modulation and are guided by the shuffle optics 11 to impinge upon the first reflector layer 25 of the I/O element 22 to form a shuffled array of outputs at the reflector and are then imaged back to the input photodetector array of the next row of EBMs.
  • This sequence is then repeated for each row of EBMs with the read beams from the final row of EAMs being guided to the output fibre array 26.
  • Figure 8 shows a block diagram of the complete processor.
  • a storage register, 33 is positioned which notionally uses electronic logic.
  • N registers store the desired matrix output port address associated with each matrix input port. Thus if input port 23 is to be connected to output port 56, the number 56 is stored in the 23rd address register.
  • the address register 33 the complete set of addresses from 1 to N is stored. If some channels are not active, then one of the unused exit port addresses is stored in its register.
  • An input buffer 32 is set in the data input line to store data during the reset intervals. This need not be very large, perhaps 20 to 30 bits per input line.
  • the processor is controlled by timing electronics 34.
  • the clock signal (CK) generated by a clock laser array 36 as previously described is removed (turn off the appropriate clock laser) and the EBM logic is designed so that it falls back to the reset state in the absence of the clock. Any row of the matrix can now be reset at will.
  • the set of N output port addresses is injected via a fibre laser input array 35 and the data path 23 in MSB first format.
  • the EBM examines addresses entering its input ports and as soon as two address bits differ, latches to the appropriate exchange or bypass state and remains there until reset. Immediately following the address bits (7 bits), the data from the buffer 32 follows. If no data is present on a line, then we may consider that channel as remaining idle. In practice it might be necessary to inject some dummy data to limit the signal disparity in the electronic EBM stages.

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  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Use Of Switch Circuits For Exchanges And Methods Of Control Of Multiplex Exchanges (AREA)
EP88301841A 1987-03-04 1988-03-02 Processeur de commutation de signal Withdrawn EP0282227A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB878705054A GB8705054D0 (en) 1987-03-04 1987-03-04 Signal switching processor
GB8705054 1987-03-04

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EP0282227A1 true EP0282227A1 (fr) 1988-09-14

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EP88301841A Withdrawn EP0282227A1 (fr) 1987-03-04 1988-03-02 Processeur de commutation de signal

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EP (1) EP0282227A1 (fr)
JP (1) JPH02502774A (fr)
AU (1) AU1360388A (fr)
GB (1) GB8705054D0 (fr)
WO (1) WO1988006828A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0385661A1 (fr) * 1989-02-24 1990-09-05 BRITISH TELECOMMUNICATIONS public limited company Réseaux de commutation optiques
EP0397372A1 (fr) * 1989-05-08 1990-11-14 AT&T Corp. Topologie de réseau pour blocage réduit et un système photonique mettant en oeuvre celle-ci
EP0397368A1 (fr) * 1989-05-08 1990-11-14 AT&T Corp. Procédé de commande d'un réseau de commutation à division spatiale
US5258978A (en) * 1989-05-08 1993-11-02 At&T Bell Laboratories Space-division switching network having reduced functionality nodes

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1987000314A1 (fr) * 1985-06-24 1987-01-15 American Telephone & Telegraph Company Agencement de permutation optique

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1987000314A1 (fr) * 1985-06-24 1987-01-15 American Telephone & Telegraph Company Agencement de permutation optique

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
IEE PROCEEDINGS, vol. 132, part J, no. 6, December 1985, pages 371-383, Hitchin, GB; J.E.MIDWINTER: "'Light' electronics, myth or reality?" *
IEEE TRANSACTIONS ON COMPUTERS, vol. C-20, no. 2, February 1971, pages 153-161, IEEE, New York, US; H.S.STONE: "Parallel processing with the perfect shuffle" *
PROCEEDINGS OF THE IEEE, vol. 72, no. 7, July 1984, pages 850-866, IEEE, New York, US; J.W.GOODMAN et al.: "Optical interconnections for VLSI systems" *
THE 6TH ANNUAL SYMPOSIUM ON COMPUTER ARCHITECTURE, 23rd-25th April 1979, Long Beach, pages 168-177, IEEE, New York, US; J.H.PATEL: "Processor-memory interconnections for multiprocessors" *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0385661A1 (fr) * 1989-02-24 1990-09-05 BRITISH TELECOMMUNICATIONS public limited company Réseaux de commutation optiques
WO1990010358A1 (fr) * 1989-02-24 1990-09-07 British Telecommunications Public Limited Company Reseaux optiques d'interconnexion
US5245458A (en) * 1989-02-24 1993-09-14 British Telecommunications Public Limited Company Optical interconnect networks
EP0397372A1 (fr) * 1989-05-08 1990-11-14 AT&T Corp. Topologie de réseau pour blocage réduit et un système photonique mettant en oeuvre celle-ci
EP0397368A1 (fr) * 1989-05-08 1990-11-14 AT&T Corp. Procédé de commande d'un réseau de commutation à division spatiale
AU618477B2 (en) * 1989-05-08 1991-12-19 American Telephone And Telegraph Company Network topology for reduced blocking and photonic system implementation thereof
US5077483A (en) * 1989-05-08 1991-12-31 At&T Bell Laboratories Network topology for reduced blocking and photonic system implementation thereof
US5122892A (en) * 1989-05-08 1992-06-16 At&T Bell Laboratories Space-division switching network having reduced functionality nodes
US5258978A (en) * 1989-05-08 1993-11-02 At&T Bell Laboratories Space-division switching network having reduced functionality nodes

Also Published As

Publication number Publication date
WO1988006828A1 (fr) 1988-09-07
AU1360388A (en) 1988-09-26
JPH02502774A (ja) 1990-08-30
GB8705054D0 (en) 1987-04-08

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