1. Introduction
With advances in optical wavelength division multiplexing (WDM) technologies and its potential of providing virtually unlimited bandwidth, optical WDM networks have been widely recognized as the dominant transport infrastructure for future Internet backbone networks[1]. One major challenge in such WDM networks has been efficient Routing and wavelength Assignment (RWA) [2]. RWA problem can be classified into static RWA and dynamic RWA problems. The static RWA is proved to be NP-hard[3]. In this paper, we formulate the static RWA problem into ILP formulation with objective to maximize the single-hop traffic in multihop network to minimize the flow delay. Basically, there are two generic approaches of RWA. The first one is to consider the RWA as a coupled problem consisting of wavelength assignment and routing problem. Generally it is a NP-hard problem. To reduce the complexity of problem, it could be decoupled into two separate subproblem. Heuristics exist for both subproblem [4], In this paper, we proposed a linear formulation for wavelength assignment problem in WDM mesh network as recently optical cross connects (OXC) systems have become available on the switching equipment side that opened up the road of possibility of deploying complex WDM network based on mesh topology[5].