Apparatus and method for large scale ATM switching

• US 5,303,078 A
• Filed: 06/22/1992
• Issued: 04/12/1994
• Est. Priority Date: 12/18/1990
• Status: Expired due to Term

• Current Assignee: TTI Inventions A LLC (Intellectual Ventures LLC)
• Original Assignee: Bell Communications Research, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Cisneros, Arturo, Brackett, Charles A.
• Primary Examiner(s): Pascal, Leslie
• Assistant Examiner(s): NEGASH, KINFE MICHAEL
• Application Number:
  US07/902,876
• Time in Patent Office: 659 Days
• Field of Search: 359/123, 359/120-121, 359/118, 359/135, 359/128, 359/139, 385/16, 385/17, 385/24, 370/60.1, 370/94.1, 370/85.2
• US Class Current: 398/51
• CPC Class Codes: H04L 12/5601 Transfer mode dependent, e.g. ATM
• CPC Class Codes: H04L 2012/561 Star, e.g. cross-connect, concentrator, subscriber group equipment, remote electronics
• CPC Class Codes: H04L 2012/5627 Fault tolerance and recovery
• CPC Class Codes: H04L 2012/5679 Arbitration or scheduling
• CPC Class Codes: H04L 2012/5681 Buffer or queue management
• CPC Class Codes: H04L 49/108 using shared central buffer
• CPC Class Codes: H04L 49/153 ATM switching fabrics having parallel switch planes
• CPC Class Codes: H04L 49/1576 Crossbar or matrix
• CPC Class Codes: H04L 49/309 Header conversion, routing tables or routing tags
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 11/0066 Provisions for optical burst or packet networks
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections
• CPC Class Codes: H04Q 2011/0009 using wavelength filters
• CPC Class Codes: H04Q 2011/0015 using splitting combining
• CPC Class Codes: H04Q 2011/0018 using tunable transmitters or receivers
• CPC Class Codes: H04Q 2011/0039 Electrical control
• CPC Class Codes: H04Q 2011/0043 Fault tolerance
• CPC Class Codes: H04Q 2011/0052 Interconnection of switches

Abstract

Apparatus and method for large scale asynchronous transfer mode (ATM) switching utilizing tunable lasers and fixed-tuned receivers are provided. The apparatus, an optical switch, includes a plurality of input modules for receiving ATM cells to be switched and a plurality of output modules for outputting the switched ATM cells. The optical switch also includes an optical transmission network for optically transmitting each ATM cell from an input module to a particular output module, and a contention resolution device in electrical communication with the plurality of input modules for selecting the ATM cells from the plurality of input modules to be switched. Preferably, each output module includes a plurality of fixed-tuned receivers and each input module includes a plurality of tunable lasers. The fixed-tuned receivers of each output module are tuned to a particular wavelength so as to pass only those ATM cells optically received from the optical transmission network at the particular wavelength. The tunable lasers are tunable to a plurality of distinct wavelengths for optically transmitting the ATM cell to the optical transmission network at the particular distinct wavelength associated with the output module to which the ATM cell is destined.

Claims

1. An optical switch for switching a succession of ATM cells, each ATM cell being received on one of a plurality of input lines and each being switched to one of a plurality of output lines to which it is directed as determined by an embedded identifier in each received cell, comprising:

a plurality of input modules, each input module connected to a different subset of the plurality of input lines and each input module comprising a buffer for sequentially storing ATM cells received on the input lines to which it is connected and a tunable laser that is tunable to a plurality of different wavelengths;

a plurality of output modules, each output module connected to a different subset of the plurality of the output lines and each output module comprising an optical receiver fixed-tuned to receive one of the plurality of different wavelengths to which the tunable lasers in the input modules and tunable;

a contention resolution device electrically connected to each of said plurality of input modules for selecting from a head of queue of ATM cells stored in the buffer of each input module at most one ATM cell to be transmitted during a cell transmission time to each output module; and

an optical star coupler connecting said input modules and said output modules for simultaneously transmitting to each output module during each cell transmission time the ATM cells selected by the contention resolution device form the head of queue of ATM cells stored in the buffers of the input modules;

the tunable laser in each input module which has an ATM cell selected to be transmitted being tuned during each cell transmission time to the wavelength associated with the receiver of the output module connected to the output line to which the selected ATM cell is directed as determined by the embedded identifier in the selected ATM cell when received by one of the input modules.

2. An optical switch in accordance with claim 1 wherein the embedded identifier in each ATM cell has a first field representing the particular output module to which it is directed, the laser in each input module being tuned in response to that first field during the cell transmission time to the wavelength associated with the fixed-tuned receiver in that particular output module.

3. The optical switch in accordance with claim 2 wherein the embedded identifier in each ATM cell has a second field representing the particular output line of the output module to which it is directed, each output module comprising means for detecting the second field in each received ATM cell and directing the received ATM cell to the output line represented in the detected second field.

4. The optical switch in accordance with claim 1 wherein each of said input modules comprises m tunable lasers, each of said output modules comprises m optical receivers, each of the m optical receivers associated with each of the output modules fixed-tuned to receive the same one of the plurality of different wavelengths to which the tunable lasers in the input modules are tunable, and said switch further comprises a total of m optical star couplers, the kth (1≦

k≦

m) star coupler connecting the kth tunable laser in each input module to the kth fixed-tuned receiver in each output module, said contention resolution device selecting form the head of queue of ATM cells stored in the buffer of each input module at most one ATM cell to be transmitted to each output module by the m tunable lasers in each input module in a time-staggered sequential manner respectively through each of the m optical star couplers.

5. The optical switch in accordance with claim 4 wherein m is less than or equal to the cell transmission time divided by a time required by the contention resolution device to select cells to be transmitted.

6. The optical switch in accordance with claim 4 wherein each one of the fixed-tuned receivers in each output module includes an optical filter for filtering wavelengths transmitted by the tunable lasers in the input modules other than the wavelength associated with that one fixed-tuned receiver, each optical filter providing for small wavelength spacing.

7. The optical switch in accordance with claim 6 wherein the optical filter included in each fixed-tuned receiver is connected to one of the optical star couplers for receiving the ATM cells transmitted by the input modules and each fixed-tuned receiver further comprises a photodiode connected to the optical filter for converting to electrical format the particular cell transmitted at the one wavelength associated with that one fixed-tuned receiver and passed through the optical filter.

8. The optical switch in accordance with claim 4 wherein each tunable laser is tunable to any one of its plurality of different wavelengths in a time substantially less than the cell transmission time, thereby providing high-speed tunability to the optical switch.

9. The optical switch in accordance with claim 8 where the tuning range is about 7 nm to about 11 nm.

10. The optical switch in accordance with claim 4 further comprising a plurality of optical preamplifiers each one separately interconnecting one of the tunable lasers and an input of one of the optical star couplers.

11. The optical switch in accordance with claim 4 further comprising a plurality of optical preamplifiers each one separately interconnecting an output of one of the optical star couplers and an input of one of the fixed-tuned receivers.

12. A method of switching a succession of ATM cells, each ATM cell being received on one of a plurality of input lines and each being switched to one of a plurality of output lines to which it is directed as determined by an identifier embedded in the received cell, different subsets of the output lines being associated with different fixed wavelengths, the method comprising the steps of:

sequentially storing the ATM cells received on different subsets of the input lines;

determining from the embedded identifier the destination subset of output lines of each ATM cell in a head of queue of stored ATM cells associated with each different subset of input lines;

resolving contention between different cells at the head of queue of stored ATM cells that are directed at the same time to output lines in the same subset of output lines so that at most only one ATM cell is selected for transmission during a cell transmission time to the same subset of output lines;

simultaneously optically transmitting to the different subsets of output lines over an optical star coupler during the cell transmission time each cell selected for transmission each at the wavelength associated with the subset of output lines to which the cell is directed as determined by the embedded identifier in the selected cell when received on one of the input lines;

in each one of the different subsets of output lines filtering all the possible different transmission wavelengths other than the one fixed wavelength associated with that one subset of output lines.

13. The method of claim 12 wherein the embedded identifier in each ATM cell has a first field representing the particular subset of output lines to which it is directed, the wavelength at which that cell is transmitted being determined form that first field.

14. The method of claim 13 wherein the embedded identifier in each ATM cell has a second field representing the particular output line in the subset of output lines to which it is directed.

15. The method of claim 12 wherein the cells are tuned to the different possible wavelengths for transmission in a time substantially less than the cell transmission time.

16. The method of claim 15 wherein the tuning range of wavelengths for transmission of cells is about 7 nm to about 11 nm.