Method for WDM optical networks including alternate routes for fault recovery

A method for routing demands on a network, wherein a plurality of rings comprising links and nodes can be logically defined in the network, each demand has a pair of endpoints at nodes of the network, each demand comprises one or more demand units, and the method comprises:

• (a) listing for each demand one or more rings that each include the endpoints of said demand;
• (b) evaluating for each listed ring a cost which depends on the occupancy of said ring by routed demand units;
• (c) selecting, for each demand unit, a ring from the pertinent list;
• and
• (d) routing working and protection paths for each demand unit on the ring selected for said demand unit;
• wherein the evaluating and selecting steps are carried out in a process that tends to minimize network cost over all routed demand units.

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.