Node architecture and design of flexible waveband routing optical networks

A novel coarse granular routing scheme for elastic optical networks is proposed in this paper, together with a node architecture and a network design algorithm. The proposed scheme allows any combination of optical paths to be routed together, and each bundle of paths, named "flexible waveband," is routed as an entity. The flexibility in bundled paths differentiates the proposed routing scheme from optical path hierarchies proposed so far and is especially appropriate for elastic optical path networks in which frequency bandwidths of optical paths are not necessarily uniform. Path bundling at each input port of a node is realized with a small port count flexible grid wavelength selective switch (WSS), while flexible waveband routing is done by other optical switches, i.e., two-stage routing. These WSSs are only responsible for the path bundling, and their degrees need not be changed even if the number of fibers connected to a node, i.e., node fiber degree, is changed. Moreover, the number of WSSs increases linearly as the node fiber degree increases. The proposed network design algorithm resolves the routing and frequency slot assignment problem while considering specific constraints imposed by the routing scheme. Numerical experiments on several real and regular topologies confirm that the routing performance degradation caused by the coarse granularity of the routing is small while the number of WSSs is substantially reduced.