Wavelength assignment in optical networks considering physical impairments

Several studies on the routing and wavelength assignment (RWA) problem have already incorporated the physical layer impairments in order to find the appropriate resources for establishing the lightpath. This approach has become known in the literature as impairment aware RWA (IA-RWA). Although it is a more realistic approach compared to the RWA, the conventional IA-RWA approach usually neglects the degradation caused by the establishment of a new lightpath in the others already established in the network. In this paper we adopted an IA-RWA approach that takes into account these degradations. From the perspective of this new approach, we conducted a performance evaluation study comparing some wavelength assignment algorithms known in the literature and a new algorithm proposed in this paper. Simulation results show that our algorithm outperforms all others evaluated.

1. INTRODUCTION

In an optical network, a lightpath interconnects two optical nodes, establishing a communication path formed by one or more concatenated links between them. A lightpath has a specific route and one or more wavelengths through which the information is routed from the source to the destination node. Several studies in the literature address the problem of choosing a route and a wavelength suitable for each lightpath by considering the optical layer as an ideal transmission media; therefore, any choice is considered to be valid from the point of view of the performance of the optical layer [1]. In practice, the optical signal suffers degradation when propagating through the fiber optic links, optical switches, optical amplifiers and other elements. With the accumulation of this degradation along the route, the bit error rate (BER) at the receiver becomes higher and can reach intolerable levels. Requirements such as sensitivity, OSNR, chromatic dispersion and PMD must be attended in order to maintain the BER at acceptable levels.