Design method for wdm optical networks including alternate routes for fault recovery

Abstract

A procedure for designing WDM optical networks provides both working circuits and protection circuits for carrying traffic demands between node pairs. The protection circuits are activated for the purpose of network recovery in case of a fault on a working circuit. Each protection circuit is link-disjoint, and preferably node-disjoint, from its corresponding working circuit. The network is subdivided into logically defined rings, such that each working and protection circuit lies on one or more of the rings. In particular embodiments of the invention, the joint routing of circuits is carried out so as to minimize the total length of the working and protection circuits according to a length that includes a weight for each link. The weight is selected to promote the efficient packing of optical fibers with wavelength channels.

1 . A method of routing demands on an optical fiber network, wherein a plurality of rings comprising links and nodes can be logically defined on the network, each demand has a pair of endpoints at respective nodes of the network, and the method comprises:
 (a) defining a working path for each demand and designating on links of the network sufficient optical fibers to support said working paths;   (b) designating, in addition to the working fibers, a set of rings of optical fibers for protection; and   (c) assigning a protection ring to each working fiber on each link;
 wherein the step of designating protection rings is carried out such that every link includes at least as many protection fibers as working fibers. 
   
     
     
         2 . The method of claim  31 , wherein the steps of designating and assigning protection rings comprise:
 (a) taking each working fiber as a one-hop demand;   (b) listing for each said demand one or more rings that each include the endpoints of said demand;   (c) evaluating for each listed ring a cost which depends on the occupancy of said ring by routed demand; and   (d) selecting, for each demand, a ring from the pertinent list, wherein the evaluating and selecting steps are carried out in a process that tends to minimize network cost over all protected demand.