Waveband switching: A new frontier in optical WDM networks

The rapid advances in dense wavelength division multiplexing (DWDM) technology with hundreds of wavelengths per fiber and world-wide fiber deployment have brought about a tremendous increase in the size (i.e., the number of ports) of photonic cross-connects, as well as in the cost and difficulty associated with controlling such large cross-connects. Waveband switching (WBS) has attracted attention for its practical importance in reducing the port count, associated control complexity, and cost of photonic cross-connects. In this chapter, we show that WBS is different from traditional wavelength routing, and thus techniques developed for wavelength-routed networks (including, for example, those for traffic grooming) cannot be directly applied to effectively address WBS-related problems. We describe a Three-layer multi-granular optical cross-connect (MG-OXC) architecture for WBS. By using this MG-OXC in conjunction with intelligent WBS algorithms, we show that one can achieve considerable savings in the port count. We present various WBS schemes and lightpath grouping strategies. Finally we discuss issues related to waveband conversion and failure recovery in WBS networks.