With the introduction of DWDM technology in telecommunication network systems, important advancements have been achieved in the problem of routing the increasing signal traffic between demand-supply nodes. The choice of the links to open, the number of links and routing of current traffic on these links in such an optical network system are important in terms of decreasing the complexity of the network and cost savings. The study in this thesis firstly introduces the use of express links, which enables those objectives, and then determines the appropriate network structure and routing. The study introduces two mathematical models as well as a lagrangian based heuristic for the solution of the problem.