Topology discovery in optical WDM networks

• US 20030058496A1
• Filed: 09/27/2001
• Published: 03/27/2003
• Est. Priority Date: 09/27/2001
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: 6766285 Canada Incorporated d/b/a Divvali Lighting Inc.
• Inventors: Neustadier, Udo Mircea, Dang, Cuong Tu, Obeda, Paul David, Nelles, David Edward, Bierman, Robert Michael
• Granted Patent: US 6,968,131 B2
• Time in Patent Office: Days
• US Class Current: 398/79
• CPC Class Codes: H04B 10/0773 Network aspects, e.g. central monitoring of transmission parameters
• CPC Class Codes: H04B 2210/071 using alarms
• CPC Class Codes: H04B 2210/074 using a superposed, over-modulated signal
• CPC Class Codes: H04J 14/0227 Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
• CPC Class Codes: H04J 14/0284 WDM mesh architectures
• CPC Class Codes: H04J 14/0287 Protection in WDM systems
• CPC Class Codes: H04Q 2011/009 Topology aspects

Abstract

In an optical WDM network, each optical channel is modulated with a respective channel identity. Detectors, conveniently at multiplex ports of optical band filters, detect the channel identities of all of the optical channels in an optical signal at the respective points to produce respective channel lists. A network management system determines channel lists for through ports of the optical band filters, identifies matching pairs of channel lists to determine a topology of each node and to identify optical paths entering or leaving each node, and identifies matching pairs of channel lists for these paths to determine an inter-node topology of the network. The channel identity detector points can alternatively be at the optical paths entering or leaving each node.

Claims

1. A method of determining topology of an optical WDM (wavelength division multiplex) network in which optical signals comprising a plurality of WDM optical channels are communicated, comprising the steps of:

modulating each optical channel with a respective signal comprising a channel identity;

detecting the channel identities of all of the optical channels in an optical signal at each of a plurality of points in the network to produce a channel list for each of said points; and

identifying matched pairs of channel lists to determine optical paths of the network between pairs of said points.

2. A method as claimed in claim 1 wherein the step of detecting channel identities comprises detecting the channel identities of all of the optical channels in an optical signal at each of a plurality of optical paths entering or leaving each of a plurality of nodes of the network.

3. A method as claimed in claim 1 wherein the step of detecting channel identities comprises detecting the channel identities of all of the optical channels in an optical signal at a multiplex port of each of a plurality of optical band filters to produce a respective channel list M, and determining a channel list T for a through port of the respective optical band filter, the channel list T comprising channels of the list M which are not within a pass band of the filter.

4. A method as claimed in claim 3 wherein the step of identifying matched pairs of channel lists comprises, for each of a plurality of nodes of the network, identifying matched pairs of channel lists among the channel lists M and T for different optical band filters of the node to determine optical paths within the node.

5. A method as claimed in claim 4 wherein the step of identifying matched pairs of channel lists further comprises, for each of the nodes, identifying any optically transparent optical band filters for which the channel lists M and T are the same, and identifying any channel lists, from among said matched pairs of channel lists of the node, matching said same channel lists M and T to determine optical connections of said optically transparent optical band filters within the node.

6. A method as claimed in claim 1 wherein the step of modulating each optical channel with a respective signal comprising a channel identity comprises variably attenuating an optical signal of the optical channel in dependence upon a signal comprising the respective channel identity.

7. A method as claimed in claim 6 wherein the signal comprising the respective channel identity has a frequency of the order of about 1 MHz or less.

8. A method of determining topology of an optical WDM (wavelength division multiplex) network in which optical signals comprising a plurality of WDM optical channels are communicated among a plurality of nodes of the network, comprising the steps of:

modulating each optical channel with a respective signal comprising a channel identity;

for each of a plurality of optical paths entering or leaving each of a plurality of nodes, determining a channel list of all the optical channels in an optical signal on the optical path, this step comprising detecting the channel identities of all of the optical channels in an optical signal at each of a plurality of points; and

identifying matching channel lists to determine optical paths of the network between the nodes.

9. A method as claimed in claim 8 wherein the step of determining a channel list of all the optical channels in an optical signal on an optical path entering or leaving a node comprises detecting the channel identities of all of the optical channels in an optical signal on the respective optical path.

10. A method as claimed in claim 8 wherein the step of determining a channel list of all the optical channels in an optical signal on an optical path entering or leaving a node comprises, for each node:

detecting the channel identities of all of the optical channels in an optical signal at a multiplex port of each of a plurality of optical band filters of the node to produce a respective channel list M;

determining a respective channel list T for an optical signal at a through port of the respective optical band filter, the channel list T comprising channels of the respective list M which are not within a pass band of the optical band filter;

identifying matching channel lists M and T to determine optical paths within the node; and

identifying unmatched channel lists M or T as channel lists for optical path entering or leaving the node.

11. A method as claimed in claim 10 wherein the step of identifying matching channel lists M and T to determine optical paths within the node comprises identifying any optically transparent optical band filters of the node for each of which the channel lists M and T are the same;

identifying matched pairs of the other channel lists M and T for the node to determine optical paths between respective ports of different optical band filters within the node; and

identifying any channel lists, from among said matched pairs of channel lists for the node, matching said same channel lists M and T to determine optical connections of said optically transparent optical band filters within the node.

12. A method as claimed in claim 8 wherein the step of modulating each optical channel with a respective signal comprising a channel identity comprises variably attenuating an optical signal of the optical channel in dependence upon a signal comprising the respective channel identity.

13. A method as claimed in claim 12 wherein the signal comprising the respective channel identity has a frequency of the order of about 1 MHz or less.

14. An optical WDM (wavelength division multiplex) network comprising a plurality of nodes and optical paths for communicating optical signals, comprising a plurality of WDM optical channels, within and among the nodes, the network comprising:

a source for each optical channel;

a modulator for modulating each optical channel with a respective signal comprising a channel identity;

a plurality of optical filters for combining optical channels to produce optical signals and for separating optical signals to derive optical channels from the optical signals;

a plurality of detectors for detecting the channel identities of all of the optical channels in an optical signal at each of a plurality of points in the network to produce a channel list for each of said points; and

a network management system for identifying matched pairs of said channel lists to determine optical paths of the network between pairs of said points.

15. An optical WDM network as claimed in claim 14 wherein the optical filters comprise optical band filters each having a multiplex port, an add or drop port, and a through port, and said plurality of points in the network comprise multiplex ports of the optical band filters.

16. An optical WDM network as claimed in claim 15 wherein the network management system is arranged to determine a channel list for a through port of an optical band filter by omitting, from optical channels of a channel list for the multiplex port of the respective optical band filter, optical channels within a pass band of the optical band filter.