The focus of this paper is on the design of the so-called Optical Wide Area Networks (OWANs), i.e., optical networks that cover broad areas. Our objective is to investigate efficient \textsc{owan} network design, where demand provisioning takes full advantage of the nodal switching equipment and of the network interface platforms under asymmetric traffic. It involves granting all traffic requests while minimizing the network capital and operational expenses, throughout an optimal dimensioning of the nodal equipment, i.e., minimizing the number and the location of the network nodal equipment. The originality of our work is in the forethought and the investigation of these issues.

We establish a mathematical model which makes use of large scale optimization tools and propose a column generation algorithm coupled with a rounding off heuristic in order to solve it efficiently. In our experiments, with different network and traffic instances, we show that a careful dimensioning and location of the nodal equipment can save up to 35% of capital expenses, and even more sometimes.