Impact of waveband switching on dimensioning multi-granular hybrid optical networks

Aggregation of wavelengths into wavebands is an attractive, cost-efficient way to facilitate switching and routing in optical networks. In this paper, we study the waveband routing and wavelength assignment (WRWA) tasks in hierarchical WDM mesh networks with optical cross-connects (OXCs) that can route multiple granularity (wavelengths and wavebands) at the same time. We present a new architecture of the OXC node and develop an integer linear programming (ILP) model of a network with those OXCs with the objective to minimize the cost of optical-electronic-optical (OEO) and all optical (OOO) ports used. The optimal ILP solution can only be obtained for networks of smaller size so that for larger problems we propose a heuristic WRWA algorithm, which solves the waveband routing and wavelength assignment sub-problems as a single problem rather than as two separate problems. Simulation results show near optimal performance of the heuristic WRWA algorithm for networks of smaller size. We comment on the WRWA performance under various OXC architectures and traffic scenarios. Our empirical studies demonstrate a significant network cost reduction that could be achieved by implementing our effective heuristic algorithm in hybrid hierarchical OXCs instead of using OXCs with optoelectronic fabric that processes single wavelengths only.