OPTICAL CROSSCONNECTS OF REDUCED COMPLEXITY FOR WDM NETWORKS WITH BIDIRECTIONAL SYMMETRY

One promising approach to provisioning and restoration in long-haul wa velength-division-multiplexing (WDM) networks is to deploy a mesh of o ptical crossconnects that operate on individual wavelengths. As wavele ngth-count and traffic demand rapidly increase, however, this approach will likely require high-port-count optical crossconnects that severe ly strain the capabilities of known device technologies. Thus, it is c ritical to devise ways to build large crossconnects from a small numbe r of constituent switches, each with reduced port count. We present a general means of accomplishing this for networks, such as current long -haul networks, that demonstrate bidirectional symmetry. We describe a broad class of symmetry-exploiting architectures that yield N x N cro ssconnects, both rearrangeably nonblocking and strictly nonblocking, u sing constituent switch fabrics no larger than N/2 x N/2. By exploitin g connection-symmetry, these architectures reduce the number of such N /2 x N/2 fabrics by 30%-50% compared with corresponding fully connecte d three-stage Benes and Clos switch structures.