Method and apparatus for locating faults in an optical network

• US 20030210908A1
• Filed: 05/10/2002
• Published: 11/13/2003
• Est. Priority Date: 05/10/2002
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Levy, David S., Mitev, Peter H.
• Granted Patent: US 7,155,123 B2
• Time in Patent Office: Days
• US Class Current: 398/33
• CPC Class Codes: H04B 10/07 Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
• CPC Class Codes: H04B 10/0791 Fault location on the transmission path
• CPC Class Codes: H04B 10/0793 Network aspects, e.g. central monitoring of transmission parameters
• CPC Class Codes: H04B 10/07953 Monitoring or measuring OSNR, BER or Q

Abstract

Method and apparatus for fault localization in an optical network using time trend correlation of end node performance parameters and intermediate node performance parameters, such as QoS and quasi-Q factors, respectively. The method and apparatus are bit-rate and protocol independent, enabling testing for each channel of a diverse dense wavelength division multiplexed traffic system using a single set of hardware.

Claims

1. A method, comprising:

monitoring optical layer performance of at least some of a plurality of network elements (NEs) forming a communications path within a communications network to extract thereby a measure of performance;

correlating a time trend for the measure of optical layer performance of each NE with a time trend of an end node performance measurement; and

identifying an underperforming NE using a respective time trend correlation.

2. The method of claim 1, wherein said measure of optical layer performance comprises performance data extracted from an eye diagram associated with a NE.

3. The method of claim 2, wherein said performance data extracted from an eye diagram comprises quasi-Q factor data.

4. The method of claim 1, wherein said end node performance measurement comprises performance data derived from a communications protocol layer.

5. The method of claim 4, wherein said communications protocol comprises one of a SONET protocol, an SDH protocol and a GigabitEthernet protocol.

6. The method of claim 1, wherein said end node performance measurement is determined using FibreChannel.

7. The method of claim 1, wherein said end node performance measurement comprises bit error rate (BER) data.

8. The method of claim 1, wherein said end node performance measurement comprises jitter data.

9. The method of claim 1, wherein said end node performance measurement comprises an optical layer performance measurement.

10. The method of claim 1, wherein:

said step of identifying an underperforming NE comprises determining that the correlation between the time trend data of respective optical layer performance and the time trend data of said end node performance measurement has diverged by a threshold amount.

11. The method of claim 10, wherein said threshold amount of divergence comprises an order of magnitude difference from a nominal correlation.

12. The method of claim 10, wherein said threshold amount is calculated as a percentage deviation from a nominal correlation level.

13. The method of claim 12, wherein said nominal correlation level is determined with respect to correlation trend data of said NE.

14. The method of claim 12, wherein said nominal correlation level is determined with respect to correlation trend data of a plurality of NEs.

20. The method of claim 1, wherein:

said step of determining a NE proximate a degradation comprises determining that the correlation between the time trend data of respective optical layer performance and the time trend data of said end node QoS performance measurement has diverged by a threshold amount.

15. A method, comprising:

monitoring optical layer performance for each of a plurality of intermediate network elements (Nes) in a communications path;

monitoring quality of service (QoS) performance for an end NE in the communications path; and

correlating time trend data for said monitored optical layer performance and said QoS performance; and

determining a NE proximate a degradation in said communications path using said changes in correlation.

16. The method of claim 15, wherein said measure of optical layer performance comprises performance data extracted from an eye diagram associated with a NE.

17. The method of claim 16, wherein said performance data extracted from an eye diagram comprises quasi-Q factor data.

18. The method of claim 15, wherein said end node performance measurement comprises at least one of a bit error rate (BER) and a jitter level.

19. The method of claim 15, wherein said end node performance measurement comprises an optical layer performance measurement.

21. A network manager for managing a plurality of network elements (NEs) in a communications system, said network manager performing the steps of:

receiving, from each of a plurality of intermediate NEs in a communications path, data indicative of respective optical layer performance;

receiving, from an end node in said communications path, data indicative of a quality of service (QoS) performance level;

correlating, for each of said plurality of intermediate NEs, time trend data of respective optical layer performance and end node QoS performance; and

in response to a degradation in said communications path, using said correlations to identify a NE proximate a degradation condition.

22. The network manager of claim 21, wherein said measure of optical layer performance comprises performance data extracted from an eye diagram associated with a NE.

23. The network manager of claim 22, wherein said performance data extracted from an eye diagram comprises quasi-Q factor data.

24. The network manager of claim 21, wherein said end node performance measurement comprises at least one of a bit error rate (BER) and a jitter level.

25. A network element (NE) adapted for use in an optical communications system, said NE having associated with it optical layer performance data, wherein deviations in time trend correlations of said optical layer performance data and quality of service (QoS) data of a communications path including said NE indicate that said NE is proximate a fault condition within said communications path.

26. A computer readable medium for storing software instructions which, when executed, perform the steps of:

receiving optical layer performance data for each of a plurality of intermediate network elements (Nes) in a communications path;

receiving quality of service (QoS) performance data for an end NE in the communications path;

correlating time trend data for said monitored optical layer performance data and said QoS performance data; and

determining a NE proximate a degradation in said communications path using said changes in said correlation.