Uniform waveband switching in WDM mesh networks

The cost of an optical network in Wavelength-Division Multiplexing (WDM) networks can be reduced by using optical add/drop multiplexers (OADMs) which allow traffic to pass through without the need for an expensive optical-electro-optical (O-E-O) conversion. OADMs can be used to add/drop specific wavelengths as in the case of fixed OADMs (FOADMs), or more flexible as in reconfigurable OADMs (ROADMs). ROADMs allow to add/drop any wavelength over a limited range or even the entire spectrum and in the case of mesh networks, multi-degree ROADMs can also switch a wavelength to other fibers. Another technique to reduce the network cost is called waveband switching (WBS). In WBS, a group of consecutive wavelengths are switched together using a single port per waveband. WBS can reduce the switching complexity of the network by reducing the number of ports per node. This results in a significant cost reduction. In this paper, we consider the problem of switching wavelengths as non-overlapping uniform wavebands for mesh networks using the minimum number of wavebands. Given a fixed band-size b_s, we give integer linear programming formulations and present a heuristic solution to minimize the number of ROADMs (number of wavebands) in mesh networks that support a given traffic pattern. We show that the number of ROADMs (or number of ports in band-switching crossconnects) can be reduced significantly in mesh networks with WBS compared to wavelength switching using either the ILP or the heuristic algorithm. We also examine the performance of our band assignment algorithms under dynamic traffic.