Performance evaluation of wavelength band switching in multifiber all-optical networks

Wavelength band switching (WBS) has only recently attracted attention from the optical networking industry for its practical importance in reducing the control complexity and cost of optical cross-connects (OXCs). However, WBS-related problems of theoretical interest have not been addressed thoroughly by the research community, and many issues are still wide open. In particular, WBS is different from wavelength routing, and thus techniques developed for wavelength-routed networks (including e.g., those for traffic grooming) cannot be directly applied to effectively address WBS-related problems. In this paper, we first propose a new multigranular OXC (MG-OXC) architecture for WBS, which is more flexible than any existing WBS node architectures. We also adopt the most powerful waveband assignment strategy, and develop an efficient heuristic algorithm called Balanced Path routing with Heavy-Traffic first (BPHT). To verify its near-optimality, we also develop an integer linear programming (ILP) model. Both the ILP and the BPHT algorithms can handle the case with multiple fibers per link and hence are more general than our previous single-fiber solutions X. Cao et al. (2002). We conduct a comprehensive evaluation of the benefits of WBS through detailed analysis and simulations. We show that the proposed heuristic BPHT can perform much better than a heuristic which applies the optimal routing and wavelength assignment (RWA) method. We also show that WBS using BPHT is even more beneficial in multifiber networks than in single-fiber networks in terms of reducing the port count. Our analytical and simulation results also provide valuable insights into the effect of wavelength band granularity, as well as the trade-offs between the wavelength-hop and the port count required in WBS networks.