Multilayer versus single-layer optical cross-connect architectures for waveband switching

Waveband switching (WBS) in conjunction with multigranular optical cross-connect (MG-OXC) architectures can reduce the cost and complexity of switching nodes. In this paper, we study two MG-OXC architectures: the single-layer and the multilayer MG-OXCs, and compare their performances with both off-line (static) and on-line (dynamic) traffic. In the off-line case, a near-optimal integer linear programming models (called off-ILP models) for each of the MG-OXC architectures aims to reduce the size of the MG-OXC, and compares them with the balanced path routing with heavy-traffic first waveband assignment (BPHT) heuristic developed for the multilayer MG-OXCs. The two architectures are then compared in terms of the number of wavelength a fixed number of wavelengths on each link. We also propose a novel efficient heuristic algorithm, called maximum overlap ratio (MOR) to satisfy new requests and compare it with the on-ILP, first-fit, and random-fit algorithms. We compare the two architectures in terms of the blocking probability, weighted (request) acceptance ratio, which serves as an indication of hops (WH) and MG-OXC ports required to satisfy a given set of traffic demands. In the on-line case, we develop an on-line ILP model called on-ILP, which aims to minimize the number of used ports for each of the MG-OXC architectures, given the revenue generated by satisfying the requests. Our results indicate that using WBS with either single-layer or multilayer MG-OXCs can reduce the number of ports (hence the size and cost) of the switching nodes compared to using ordinary OXCs (without waveband switching). In particular, in the off-line case, using single-layer MG-OXCs provides a greater reduction in size than multilayer MG-OXCs, while in the online case, using the multilayer MG-OXC is better.