Method and apparatus for performance management of a multiplexed transmission system

• US 6,735,725 B1
• Filed: 09/29/2000
• Issued: 05/11/2004
• Est. Priority Date: 09/29/2000
• Status: Expired due to Term

• Current Assignee: Ciena Corporation
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Wan, Ping W., Wu, Chung Y.
• Primary Examiner(s): Decady, Albert
• Assistant Examiner(s): Torres, Joseph D
• Application Number:
  US09/672,789
• Time in Patent Office: 1,320 Days
• Field of Search: 714/704, 714/708, 714/752
• US Class Current: 714/704
• CPC Class Codes: H04J 14/0221 Power control, e.g. to keep the total optical power constant
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04W 52/20 using error rate
• CPC Class Codes: H04W 52/34 TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment

Abstract

A method and apparatus for performing optical channel performance management on a WDM system while in operation is disclosed in which each transmitter and receiver uses forward error-correction schemes to improve the BER performance of the channel in a known relation to the performance before error-correction. The receiver measures the BER performance before error-correction in real-time and communicates it to a system manager which determines, from this data, the appropriate launch power of each transmitter in the system, which it commands each transmitter to adopt, thereby ensuring relative launch powers which optimize the overall BER performance of the WDM multiplexed signal.

Claims

1. A method of equalizing performance of a composite channel made up of a plurality of parallel multiplexed transmission channels comprising:

i) receiving a corresponding parallel plurality of forward error encoded signals from the composite channel;

ii) determining a first plurality of Bit-Error-Rate (BERu) values for the corresponding parallel plurality of encoded signals received from the composite channel, wherein the first plurality of BERu values is determined prior to an application of forward error correction on any one of the corresponding parallel plurality of forward error encoded signals;

iii) signalling for individual adjustment of each of a plurality of transmission powers over the plurality of parallel multiplexed transmission channels, respectively, based on the first plurality of BERu values, so as to equalize subsequent pluralities of BERU values; and

iv) applying forward error correction decoding on each of the corresponding parallel plurality of forward error encoded signals received from the composite channel; and

v) determining a second plurality of Bit-Error-Rate (BERc) values after the application of forward error correction decoding on each of the corresponding parallel plurality of forward error encoded signals;

wherein the forward error correction provides an improvement between the first plurality of BERu values and the second plurality of BERc values in a known relation respectively.

2. The method according to claim 1, wherein a type of forward error correction code used is a Reed-Solomon code.

3. A method of equalizing performance of a composite channel made up of a plurality of a parallel multiplexed transmission channels comprising:

i) setting a respective equalization target for each of the plurality of parallel multiplexed transmission channels;

ii) determining a respective Bit-Error Rate (BERu) value for each of a plurality of encoded signals received from the plurality of parallel multiplexed transmission channels, wherein the respective BERu values are determined before an application of forward error correction on any of the plurality of encoded signals received from the plurality of parallel multiplexed transmission channels;

iii) calculating a respective ratio for each of the plurality of encoded signals received, wherein each ratio is a ratio of the respective equalization target to the respective BERu value for a respective one of the plurality of parallel multiplexed transmission channels;

iv) comparing each ratio so calculated in step iii) to determine whether or not all of the ratios are greater than 1, and

if all of the ratios are greater than 1 equalization is achieved and the method terminates here;

but if not,

v) identifying a worst performing channel as the one of the plurality of parallel multiplexed transmission channels with a lowest ratio calculated in step iii) and

if the worst performing channel has a ratio greater than 1 reverting to step ii);

but if not,

vi) increasing the power of the worst performing channel by a pre-determined amount;

vii) calculating an updated value of the BERu value for the worst performing channel and an updated ratio of the respective equalization target for the worst performing channel to said updated value of the BERu value; and

viii) comparing the updated ratio calculated in step vii) to the respective ratio calculated in step iii) for the worst performing channel to determine whether or not said updated ratio is less than said respective ratio calculated in step iii) and

if said updated ratio is less than said respective ratio calculated in step iii), terminating the method here;

but if not reverting to step ii).

4. A computer-readable medium storing computer executable program instructions which, when executed by a processor in a receiver in a communications system, causes the receiver to:

i) set a respective equalization target for each of the plurality of parallel multiplexed transmission channels;

ii) determine a respective of Bit Error Rate (BERu) value for each of a plurality of encoded signals received from the plurality of parallel multiplexed transmission channels, wherein the respective BERu values are determined before an application of forward error correction on any of the plurality of encoded signals received from the plurality of parallel multiplexed transmission channels;

iii) calculate a respective ratio for each of the plurality of encoded signals received, wherein each ratio is a ratio of the respective equalization target to the respective BERu value for a respective one of the plurality of parallel multiplexed transmission channels;

iv) compare each ratio so calculated in step iii) to determine whether or not all of the ratios are greater than 1, and

if all of the ratios are greater than 1 equalization is achieved and the method terminates here;

but if not,

v) identify a worst performing channel as the one of the plurality of parallel multiplexed transmission channels with a lowest ratio calculated in step iii) and

if the worst performing channel has a ratio greater than 1 reverting to step ii);

but if not,

vi) increase the power of the worst performing channel by a pre-determined amount;

vii) calculate an updated value of the BERu value for the worst performing channel and an updated ratio of the respective equalization target for the worst performing channel to said updated value of the BERu value; and

viii) compare the updated ratio calculated in step vii) to the respective ratio calculated in step iii) for the worst performing channel to determine whether or not said updated ratio is less than said respective ratio calculated in step iii) and

if said updated ratio is less than said respective ratio calculated in step iii), terminate the method here;

but if not revert to step ii).