We propose an in-depth study of the reconfiguration problem in multi-fiber WDM networks. It consists in defining how to adapt the optical layer to changing traffic patterns. Our objective is to treat the problem globally. We consider arbitrary mesh topology, all-to-all traffic and multi-hop routing. However, we restrict ourselves to prevision: the traffic evolutions are foreseen. We propose a compact Mixed Integer Linear Programming model, allowing to solve medium instances. We define many metrics to evaluate the performance of a solution. We also propose some mathematical cuts and a lower bound for the problem. We make extensive experiments based on this model, in order to find out the influence of different parameters, such as the metric chosen or the cut formulation. To do so, many instances were solved with different networks.