Wavelength assignment in route-fixed optical WDM ring by a branch-and-price algorithm

This paper addresses the wavelength assignment problem (WAP) in optical wavelength division multiplexed (WDM) telecommunication networks. We show that, even though WAP on optical ring topology belongs to NP-hard, WAP can be exactly solvable in practical size optical WDM rings for current and future traffic demand. To accomplish this, we convert WAP to the vertex coloring problem of the related graph and choose a special integer programming formulation for the vertex coloring problem. We develop a branch-and-price algorithm for the problem and carry out the performance comparison of the suggested algorithm with a well-known heuristics.