This article presents a mathematical model that results in a low-cost network design to satisfy a set of point-to-point demands that arrive and leave the network along of time. It considers the problem of routing working traffic and assigning wavelengths in an all-optical network avoiding if possible that wavelengths assignment changes and flow rerouting. The model allows to know when a reconfiguration/expansion is needed. The model provides a physical network configuration selecting a lowest cost set of components of the network (subnetworks and OXCs) with sufficient capacities to attend the demands and the required wavelengths in all time.