Optical packet switching apparatus and methods

• US 7,218,853 B2
• Filed: 08/01/2006
• Issued: 05/15/2007
• Est. Priority Date: 09/04/2001
• Status: Expired due to Term

• Current Assignee: F Poszat Hu LLC (Intellectual Ventures LLC)
• Original Assignee: Doron Handelman
• Inventors: Handelman, Doron
• Primary Examiner(s): Chan; Jason
• Assistant Examiner(s): CURS, NATHAN M
• Application Number:
  US11/461,459
• Publication Number:
  US 20060263088A1
• Time in Patent Office: 287 Days
• Field of Search: 398 49- 51, 398 45- 59, 370/48, 370/465, 370/477, 370/230, 370/230.1, 370/231, 370/232, 370/235
• US Class Current: 398/51
• CPC Class Codes: H04J 14/08 Time-division multiplex systems
• 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 2011/0015 using splitting combining
• CPC Class Codes: H04Q 2011/0035 using miscellaneous components, e.g. circulator, polarisation, acousto/thermo optical
• CPC Class Codes: H04Q 2011/005 Arbitration and scheduling
• CPC Class Codes: H04Q 2011/0064 Arbitration, scheduling or medium access control aspects
• CPC Class Codes: H04Q 2011/0075 Wavelength grouping or hierarchical aspects
• CPC Class Codes: H04Q 2011/0084 Quality of service aspects

Abstract

An optical packet switch switches optical packets according to bit-rates at which the optical packets are provided. For example, optical packets that are received at similar bit-rates may be routed to a destination at separate time slots over a single channel wavelength, and optical packets that are received at different bit-rates may be routed to the destination over separate channel wavelengths. When optical packets are provided at different bit-rates on a plurality of input paths, optical packets provided at low bit-rates may be compacted before switching to the destination. Alternatively or additionally, the bit-rates of the optical packets may be balanced before switching to the destination. Bandwidth contention among optical packets may be resolved by polarizing optical packets originating from separate input paths in different polarization directions, and merging optical packets having different polarization directions onto a single switched channel wavelength. Compaction of optical packets may alternatively be employed for resolution of bandwidth contention. Related apparatus and methods are also described.

Claims

1. A method of resolving bandwidth contention between a first optical packet arriving on a first path and a second optical packet arriving on a second path, the method comprising:

determining that the bandwidth contention can be resolved by compaction of both the first optical packet and the second optical packet;

compacting the first optical packet and the second optical packet by different compaction factors in response to said determining; and

switching the first optical packet and the second optical packet, both being in a compacted form, to a destination on a single switched channel wavelength.

2. The method according to claim 1 and wherein each of said first optical packet and said second optical packet comprises one of the following:

a fixed-length optical packet; and

a variable-length optical packet.

3. The method according to claim 1 and also comprising updating the destination of said compacting.

4. The method according to claim 1 and also comprising routing a replica of at least one of the following to monitoring circuitry:

the first optical packet;

the second optical packet;

a compacted form of the first optical packet; and

a compacted form of the second optical packet.

5. The method according to claim 1 and wherein each of the first optical packet and the second optical packet is coded by a line code.

6. The method according to claim 5 and wherein the line code comprises one of the following:

a return-to-zero (RZ) line code; and

a non-return-to-zero (NRZ) line code.

7. A method of resolving bandwidth contention between a first optical packet arriving on a first path and a second optical packet arriving on a second path, the method comprising:

determining that the bandwidth contention can be resolved by compaction of at least one of the first optical packet and the second optical packet, the determining comprising determining a compaction factor, said determining a compaction factor comprising;

obtaining a bit-rate identifier comprised in a header associated with an optical packet which is to be compacted, the bit-rate identifier identifying a first bit-rate;

obtaining a bit-rate identifier comprised in a header associated with an optical packet which is not to be compacted, the bit-rate identifier identifying a second bit-rate; and

dividing the second bit-rate by the first bit-rate to obtain the compaction factor;

compacting said at least one of the first optical packet and the second optical packet by said compaction factor in response to said determining; and

switching the first optical packet and the second optical packet, at least one of which being in a compacted form, to a destination on a single switched channel wavelength.

8. The method according to claim 7 and wherein the compacting comprises:

converting the at least one of the first optical packet and the second optical packet to electronic signals at a first bit-rate;

extracting, from the electronic signals at the first bit-rate, a first clock signal;

multiplying the first clock signal by the compaction factor, thereby generating a second clock signal;

employing the second clock signal and the electronic signals at the first bit-rate to generate electronic signals at a second bit-rate; and

converting the electronic signals at the second bit-rate to at least one optical packet at the second bit-rate.

9. The method according to claim 7 and wherein each of said first optical packet and said second optical packet comprises one of the following:

a fixed-length optical packet; and

a variable-length optical packet.

10. The method according to claim 7 and wherein each of the first optical packet and the second optical packet is coded by a line code.

11. The method according to claim 10 and wherein the line code comprises one of the following:

a return-to-zero (RZ) line code; and

a non-return-to-zero (NRZ) line code.

12. Apparatus for resolving bandwidth contention between a first optical packet arriving on a first path and a second optical packet arriving on a second path, the apparatus comprising:

a switching/routing control unit operative to generate a determination that the bandwidth contention can be resolved by compaction of at least one of the first optical packet and the second optical packet;

at least one packet compactor operatively controlled by said switching/routing control unit and operative to compact said at least one of the first optical packet and the second optical packet in accordance with said determination;

at least one switching node operatively controlled by said switching/routing control unit and operative to switch the first optical packet and the second optical packet, at least one of which being in a compacted form, to a destination on a single switched channel wavelength; and

monitoring circuitry operative to employ replicas of optical packets before compaction/expansion and replicas of optical packets after compaction/expansion provided thereto to perform at least one of the following;

monitor compaction/expansion of optical packets;

detect loss of optical packets; and

detect compaction/expansion errors.

13. The apparatus according to claim 12 and wherein the at least one packet compactor is operative to compact the at least one of the first optical packet and the second optical packet by a compaction factor, and the switching/routing control unit is operative to select the compaction factor.

14. Apparatus according to claim 12 and wherein each of said first optical packet and said second optical packet comprises one of the following:

a fixed-length optical packet; and

a variable-length optical packet.

15. Apparatus for resolving bandwidth contention between a first optical packet arriving on a first path and a second optical packet arriving on a second path, the apparatus comprising:

a switching/routing control unit operative to generate a determination that the bandwidth contention can be resolved by compaction of at least one of the first optical packet and the second optical packet;

at least one packet compactor operatively controlled by said switching/routing control unit and operative to compact said at least one of the first optical packet and the second optical packet in accordance with said determination, the at least one packet compactor comprising;

an optical receiver operative to convert said at least one of the first optical packet and the second optical packet to electronic signals at a first bit-rate;

a clock multiplication/division unit operative to extract a first clock signal from the electronic signals generated by the optical receiver, and to multiply the first clock signal by a pre-selected compaction factor, thereby generating a second clock signal;

a buffer operative to receive the second clock signal and the electronic signals generated by the optical receiver and to output electronic signals at a second bit-rate; and

an optical transmitter driven by the electronic signals at the second bit-rate to generate at least one optical packet at the second bit-rate; and

at least one switching node operatively controlled by said switching/routing control unit and operative to switch the first optical packet and the second optical packet, at least one of which being in a compacted form, to a destination on a single switched channel wavelength.

16. Apparatus according to claim 15 and wherein the switching/routing control unit is operative to pre-select the compaction factor.

17. Apparatus according to claim 15 and wherein each of said first optical packet and said second optical packet comprises one of the following:

a fixed-length optical packet; and

a variable-length optical packet.

18. Apparatus for resolving bandwidth contention between a first optical packet arriving on a first path and a second optical packet arriving on a second path, the apparatus comprising:

a switching/routing control unit operative to generate a determination that the bandwidth contention can be resolved by compaction of both the first optical packet and the second optical packet;

at least one packet compactor operatively controlled by said switching/routing control unit and operative to compact the first optical packet and the second optical packet by different compaction factors in response to the determination; and

at least one switching node operatively controlled by the switching/routing control unit and operative to switch the first optical packet and the second optical packet, both being in a compacted form, to a destination on a single switched channel wavelength.

19. Apparatus for resolving bandwidth contention between a first optical packet arriving on a first path and a second optical packet arriving on a second path, the apparatus comprising:

a switching/routing control unit operative to generate a determination that the bandwidth contention can be resolved by compaction of at least one of the first optical packet and the second optical packet, the determination comprising a determination of a compaction factor, and the switching/routing control unit is also operative, for determining the compaction factor;

to obtain a bit-rate identifier comprised in a header associated with an optical packet which is to be compacted, the bit-rate identifier identifying a first bit-rate;

to obtain a bit-rate identifier comprised in a header associated with an optical packet which is not to be compacted, the bit-rate identifier identifying a second bit-rate; and

to divide the second bit-rate by the first bit-rate to obtain the compaction factor;

at least one packet compactor operatively controlled by said switching/routing control unit and operative to compact said at least one of the first optical packet and the second optical packet by said compaction factor in response to said determination; and

at least one switching node operatively controlled by said switching/routing control unit and operative to switch the first optical packet and the second optical packet, at least one of which being in a compacted form, to a destination on a single switched channel wavelength.

20. A method of resolving bandwidth contention between a first optical packet arriving on a first path and a second optical packet arriving on a second path, the method comprising:

generating a determination that the bandwidth contention can be resolved by compaction of at least one of the first optical packet and the second optical packet;

compacting said at least one of the first optical packet and the second optical packet in accordance with said determination, the compacting comprising;

converting said at least one of the first optical packet and the second optical packet to electronic signals at a first bit-rate;

extracting, from the electronic signals at the first bit-rate, a first clock signal and multiplying the first clock signal by a pre-selected compaction factor, thereby generating a second clock signal;

receiving the second clock signal and the electronic signals at the first bit-rate and outputting electronic signals at a second bit-rate; and

using the electronic signals at the second bit-rate to drive an optical transmitter for generating at least one optical packet at the second bit-rate; and

switching the first optical packet and the second optical packet, at least one of which being in a compacted form, to a destination on a single switched channel wavelength.