Utilize 100% redundancy to offer higher-level multiple fault restoration in WDM networks without wavelength conversion

This study addresses the problem of achieving higher-level multi-fault restoration in wavelength division multiplexing (WDM) networks with no wavelength conversion capability. A heuristic scheme, designated as the Directional Cycle Decomposition Algorithm (DCDA), is developed to maximize the number of tolerable faults utilizing only 100% redundancy in WDM networks without wavelength conversion. The redundancy is calculated as the required spare capacity over the given working capacity. The process of identifying the maximum number of tolerable faults is modeled as a constrained ring cover set problem. DCDA decomposes this problem into three steps and has an overall computational complexity of O(∣E∣∣V∣(C + 1) + ∣E∣(C2 + 1)), where ∣V∣, ∣E∣ and C represent the number of vertices, the number of edges in the graph and the number of cycles in the cycle cover, respectively. The evaluation results reveal that the average number of tolerable simultaneous faults increases considerably under DCDA and the maximum number of tolerable simultaneous faults approaches the optimal solution provided by the brute-force method. DCDA facilitates an improved best-effort multi-fault restorability for a variety of planar and non-planar network topologies. An analytical method is proposed to facilitate a rapid estimation of the multi-fault restorability in a network using DCDA without the need for experimental evaluations. In addition, an approximation method is developed to obtain an estimate of the multi-fault restorability directly from DCDA without the requirement for a detailed knowledge of the network topology and restoration routes. The results show that the average errors in the approximated restorability values obtained using this method range from 0.12% (New Jersey) to 1.58% (Cost 239).