Path-protection routing and wavelength assignment in WDM mesh networks under shared-risk-group constraints

Abstract

This study investigates the problem of fault management in a wavelength-division multiplexing (WDM)-based optical mesh network in which failures occur due to fiber cuts. In reality, bundles of fibers often get cut at the same time due to construction or destructive natural events, such as earthquakes. Fibers laid down in the same duct have a significant probability to fail at the same time. If two fibers reside in the same cable (bundle of fibers) or the same duct, we say that these two fibers are in the same Shared Risk Group (SRG). When path protection is employed, we require the primary path and the backup path to be SRG-disjoint, so that the network is survivable under single-SRG failures. Moreover, if two primary paths go through any common SRG, their backup paths cannot share wavelengths on common links. This study addresses the routing and wavelength-assignment problem in a network with path protection under SRG constraints. Off-line algorithms for static traffic is developed to combat single-SRG failures. The objective is to minimize total number of wavelengths used on all the links in the network. Both Integer Linear Programs (ILPs) and heuristic algorithms are presented and their performances are compared through numerical examples.