Abstract: “Wavelength Division Multiplexing (WDM) technology is employed in fiber-optic communication systems to multiplex optical carrier signals to a single optical fiber using different wavelengths. Fault tolerance is an important parameter in WDM networks. When a fault occurs the network requires a fault tolerance technique to repair the fault. In this paper, a new fault tolerance technique is proposed for the load balancing routing and wavelength assignment (RWA) problem. In RWA problem the fault protection issue is alienated to fault tolerant routing and fault tolerant wavelength assignment for traffic in WDM networks. The wavelength assignment is done using an advanced reservation algorithm. In routing, the primary path is set by applying max-flow load balancing technique. Then a backup path is computed for handling the link failures based on the class of request. The backup path is used for link restoration when primary path fails. Based on the class, we find the available bandwidth for b”

Keywords: WDM networks, Fault Tolerance, Routing and Wavelength Assignment (RWA)