Removal of Loop Back in p-cycle Protection: Second Phase Reconfiguration

P-cycles are one of the most promising techniques of span protection used in optical networks. However the protection path provided by p-cycle may contain some nodes, which are part of the working path also. When the p-cycle is used to provide protection to any failed span of the working path, then due to the common nodes in working path and protection path provided by p-cycle, there will be overlapping of these nodes in the restored path. These overlapping nodes will appear twice in the restored path, once in the working path and then in the protection path provided by p-cycle for the protection of any failed span. This repetition will make loops at the overlapping nodes. Hence redundant span capacity will be used. To remove these loops, and release the redundant capacity a scheme is developed to reconfigure the restored path. This aspect of the p-cycle has not been discussed so far in the literature. The released capacity is calculated and it has been found that significant amount of capacity is released. The average amount of released capacity with second phase reconfiguration, is in the range of 26% to 28% for the test network, depending upon the traffic distribution