A wavelength routed optical network is considered for which the traffic matrix and possibly the physical topology are different during different periods of a time horizon. The optimal virtual topology for each of the periods is different. Rather than using the best topology in every period and incurring a possibly significant reconfiguration cost, it is necessary to consider the optimum sequence of virtual topologies that will minimise the sum of the operating and reconfiguration costs over the entire horizon. The presence of short-term cycles in the traffic pattern and the possible evolution of resources and demand in the network motivates this work. The approach adopted is to find a ranked set of virtual topologies for each period and then define a shortest path problem to obtain the optimum sequence. Examples on a 10 node section of the NSFNET topology are presented.
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