Comparison of OXC node architectures for WDM and flex-grid optical networks

Optical networks form the core of the Internet's backbone today. The constantly increasing traffic demands require large scale optical cross-connects (OXCs) with high port-counts and line capacities. Currently, wavelength-selective switches (WSS) are utilized to create the OXCs. However, the port count of commercially available WSSs is limited. To achieve high port counts in OXCs, the existing WSS-based approach is to cascade WSSs, which results in a square order increment in the number of required WSSs. To save the hardware costs in terms of number of WSSs, two novel OXC architectures utilizing the waveband switching technique have been proposed. These architectures are not only applicable to conventional fixed-grid wavelength division multiplexing (WDM) networks, but they are also applicable to emerging flex-grid elastic optical networks. In this paper, we conduct a detailed comparison among the conventional cascading architecture and the two new architectures. We propose algorithms to accommodate dynamic traffic demands for all architectures and compare the blocking rates. The results show that the blocking rates of the new architectures are very small and close to that of the cascading architecture, while having much smaller node complexity.