In this paper, we consider the problem of multicast routing and wavelength assignment (MC-RWA) in multi-fiber all-optical WDM networks. Two main network design system comprehensively investigated here are mesh and multi-ring designs. Given the multicast traffic demands, we present new ILP formulations to solve the MC-RWA problem with an objective to determine the minimal number of fibers needed to support the multicast requests. Unlike previous studies, our ILP formulations are not only capable of finding the optimal multicast routing and wavelength assignment pattern to the light-trees, but also finding the optimal light-tree structures simultaneously. Since broadcast and unicast communications are special cases of multicast communications, our ILP models are actually the generalized RWA mathematical models of optical WDM networks. In addition to proposing the ILP models, this paper takes two main issues affecting the network capacity requirement into account, that is, the splitting degree level of optical splitters and techniques of wavelength assignment to the light-trees. Three multicast wavelength assignment techniques studied in this paper are Light-Tree (LT), Virtual Light-Tree (VLT) and Partial Virtual Light-Tree (PVLT) techniques. Due to the NP-completeness of the MC-RWA problem, the ILP formulations can reasonably cope with small and moderate networks. To work with large networks, this paper presents alternative MC-RWA ILP-based heuristic algorithms for the PVLT and LT networks and develops lower bound techniques to characterize the performance of our algorithms. Using existing large backbone networks, numerical results are reported to analyze such aspects as multiple fiber systems, the benefits of using optical splitters and wavelength converters, and the capacity difference between the mesh and multi-ring designs. Finally, this paper provides an analysis of the influence of network connectivity on the network implementation under the constraints of mesh and multi-ring design schemes.

This paper presents a comprehensive investigation of three optical wavelength-division multiplexed (WDM) mesh network protection approaches, namely minimal cost, single link basis and disjoint path approaches. The operation of each approach is described and their performances are extensively evaluated and compared. Key aspects that are taken into the consideration and comparison of the designs include a spare capacity requirement, ease of operation and practical feasibility. A mathematical model based on integer linear programming is introduced to obtain a lower bound on the spare capacity requirement for full protection against all single link failures. Two heuristic algorithms have also been developed to perform wavelength resource allocation under both normal and failure conditions for both systems with and without wavelength conversion capability. It is shown that the minimal cost approach can accomplish the lowest extra cost requirement for protection, but this approach is considered not appropriate for practical applications due to complicated restoration and management. The single link basis scheme is on the other hand more practical and very cost efficient. For the disjoint path technique, the cost for spare capacity is generally slightly greater than that of the single link basis scheme. Its main advantages lie in the simple re-configuration and inherent protection against node failure for in-transit traffic. Finally, a new framework for obtaining a good spare capacity cost estimate of a mesh restorable network is presented.

In this paper, two distinct optical network design approaches, namely mesh and multi-ring, for survivable WDM networks are investigated. The main objective is to compare these two design approaches in terms of network costs so that their merits in practical environments can be identified. In the mesh network design, a new mathematical model based on integer liner programming (ILP) and a heuristic algorithm are presented for achieving a minimal cost network design. In the multi-ring network design, a heuristic algorithm that can be applied to large network problems is proposed. The influence of wavelength conversion and the number of wavelengths multiplexed in a fiber on system designs are also discussed. Based on the simulation results, the redundancy quantities required for full protection in multi-ring approach are significantly larger in comparison to the minimal cost mesh counterpart.