Survivable Lightpath Provisioning in WDM Mesh Networks Under Shared Path Protection and Signal Quality Constraints

This paper addresses the problem of survivable lightpath provisioning in wavelength-division-multiplexing (WDM) mesh networks, taking into consideration optical-layer protection and some realistic optical signal quality constraints. The investigated networks use sparsely placed optical–electrical–optical (O/E/O) modules for regeneration and wavelength conversion. Given a fixed network topology with a number of sparsely placed O/E/O modules and a set of connection requests, a pair of link-disjoint lightpaths is established for each connection. Due to physical impairments and wavelength continuity, both the working and protection lightpaths need to be regenerated at some intermediate nodes to overcome signal quality degradation and wavelength contention. In the present paper, resource-efficient provisioning solutions are achieved with the objective of maximizing resource sharing. The authors propose a resource-sharing scheme that supports three kinds of resource-sharing scenarios, including a conventional wavelength-link sharing scenario, which shares wavelength links between protection lightpaths, and two new scenarios, which share O/E/O modules between protection lightpaths and between working and protection lightpaths. An integer linear programming (ILP)-based solution approach is used to find optimal solutions. The authors also propose a local optimization heuristic approach and a tabu search heuristic approach to solve this problem for real-world, large mesh networks. Numerical results show that our solution approaches work well under a variety of network settings and achieves a high level of resource-sharing rates (over 60% for O/E/O modules and over 30% for wavelength links), which translate into great savings in network costs.

Transparent vs. Opaque vs. Translucent Wavelength-Routed Optical Networks

A wavelength-routed optical network consists of multi-wavelength crossconnect switches (XCSs) which are interconnected by optical fibers. Some (or all) crossconnects, referred to as nodes in this paper, are also attached to access stations where data from several end-users could be multiplexed onto a single wavelength division multiplexed (WDM) channel. An access station provides optical-to-electronic (O/E) conversion and wice wersa to interface the optical network with conventional electronic equipment. The access station, at an intermediate node, may also be used (as in this study) for signal regenerution on a lightpath. A new call is admitted into the network if a lightpath (a set of free wavelengths along a given route from source to destination) can be established between the call’s source and destination stations. Depending on the number of all-optical fragments in a single lightpath, three different approaches may be employed to operate such a network. These approaches are: transparency, opacity, and translucency (to be explained below). Our study concentrates on evaluating the relative merits of these three approaches in a sample network environment.