<title>Blocking performance analysis of fixed-paths least-congestion routing in multifiber WDM networks</title>

Abstract

Wavelength-routed all-optical networks have been receiving significant attention for high-capacity transport applications. A good routing and wavelength assignment (RWA) algorithm is critically important to improve the performance of wavelength-routed WDM networks. We study the blocking performance of fixed-paths least-congestion (FPLC) routing in multifiber WDM networks in this paper. A new analytical model based on the link-load correlation is developed to evaluate the blocking performance of the FPLC routing. The analytical model is a generalized model that can be used in both regular (e.g. mesh-torus) and irregular (e.g. NSFnet) networks. It is shown that the analytical results closely match the simulation results, which indicates that the model is adequate in analytically predicting the performance of the FPLC routing in different networks. Multifiber WDM networks offer the advantage of reducing the effect of the wavelength continuity constraint without using wavelength converters. A wavelength that cannot continue on the next hop on the same fiber can be switched to another fiber using an optical cross-connect (OXC) if the same wavelength is free on one of the other fibers. However, the cost of a multifiber network is likely to be higher than a single-fiber network with the same capacity, because more amplifiers and multiplexer/demultiplexer may be required. The design goal of a multifiber network is to achieve high network performance with the minimum number of fibers. Two FPLC routing algorithms, wavelength trunk (WT)-based FPLC and lightpath (LP)-based FPLC, are proposed and studied. Our analytical and simulation results show that the LP-based FPLC routing algorithm can use multiple fibers more efficiently than the WT-based FPLC and the alternate path routing. In both the mesh-torus and NSFnet networks, limited number of fibers is sufficient to guarantee high network performance.