Wavelength Retuning in Optical Waveband Switching Networks

To address the challenge of the node-size (i.e., number of ports in the switching fabric) increase faced by the wavelength routed networks (WRNs), waveband switching (WBS) is introduced to group multiple wavelengths together as a band or fiber and switch them using a single port whenever possible. In WBS networks with dynamic traffic, one important goal is to minimize the traffic blocking probability, which can be caused by two factors: shortage of wavelengths and limited number of switching ports. In this work, for the first time, we study wavelength retuning in WBS networks, which was used in WRNs to reduce the traffic blocking caused by the wavelength shortage. We analyze the unique features of wavelength retuning in WBS networks as well as the various cases of port consumption due to wavelength retuning. Two strategies, namely, Inter-band retuning and Intra-band retuning are introduced to reduce the blocking caused by both the wavelength continuity constraint and the port shortage. We also propose a new wavelength retuning scheme, namely port-aware wavelength retuning (PAWR), which seeks a compromise between these two strategies and takes the advantage of both. Our simulations show that the proposed schemes can effectively reduce the blocking probability in WBS networks by as much as 20%.