Improved double cycle and link pair methods for two-link failure protection

In this paper, we have proposed Link Pair Method (LPM) and Improved Double Cycle (IDB) method based on pre-Configured Cycles (p-cycles) for two-link failure protection in optical networks. We have compared Double Cycle (DB), IDB and LPM method on the basis of spare capacity and computation time. We have observed a reduction in the required spare capacity for IDB as compared to the DB method. We achieved this reduction by assigning priority to the p-cycles of the protection pair for each link. We also found that assigning priority reduces the number of variables and constraints required to formulate the integer linear program of IDB as compared to the DB method thereby reducing the computational resources. The LPM method considers all the possible pair of links in the optical network and selects the non-intersecting sets of p-cycles for each pair of links. Our complexity analysis and simulation result shows that the LPM requires significantly less number of variables and computational time compared to the DB and IDB methods. We also show that LPM method is capable to compute spare capacity of larger networks for which DB and IDB methods fail.