An Exact ILP Formulation for Optimal Wavelength Converter Usage and Placement in WDM Networks

In WDM all-optical networks, the use of wavelength converters can increase the wavelength resource efficiency and reduce the blocking probability. However, all-optical wavelength converters are likely to remain costly devices. Moreover, the blocking probability does not decrease linearly with the number of converters. Hence, it is desirable that just a limited amount of wavelength converters are used in the whole network. In this case, a vital question arises: how many converters are enough and where to place these converters? In this paper, we introduce for the first time an exact ILP formulation to minimize the number of necessary wavelength converters as well as to place these converters in the network for a static traffic pattern, when its Routing Wavelength Assignment (RWA) is infeasible if no wavelength converter is used but feasible if the wavelength continuity constraint is relaxed. By running the optimization for numerous different random traffic patterns, we can at the end find the nodes with highest probability to place wavelength converters.