Restoration from multiple faults in WDM networks without wavelength conversion

This paper addresses the problem of achieving full and fast restoration to tolerate as many faults as possible in wavelength-routed wavelength division multiplexing (WDM) networks with no wavelength conversion. We model the problem of finding the maximum number of faults tolerated as a constrained ring cover problem, which is a decomposition problem of exponential complexity. Three heuristic methods which guarantee that at least one fault can be tolerated are proposed. The Ear Decomposition (ED) method can always generate a decomposition to guarantee that only one fault can be tolerated. The Planar Decomposition (PD) method, which takes advantage of the bipartite graph model to generate a decomposition, can tolerate up to f faults, where f is the maximum cardinality between the two bipartite vertex sets. The Maximally Separated Rings (MSR) method uses the greedy method to find a decomposition to tolerate as many faults as possible. The marked-link (ML) method is also proposed to enhance the performance by marking some links, which are originally used for protection, available for normal transmissions. Finally, we also evaluate the number of faults tolerated and the blocking probabilities of these methods in three example networks.