An ILP Formulation for Partially Upgrading Elastic Optical Networks to Multi-Band

We propose an integer linear programming (ILP) formulation to perform a partial upgrade of conventional elastic optical networks to multi-band optical networks in which both the C-band and the L-band are activated. Under the assumption that, in dynamic network operation, the optical connections are established following precomputed paths, the formulation determines which (limited) set of fibers should be upgraded to support multi-band transmission with the objective of maximizing the number of precomputed paths that can benefit from such upgrade. We investigate the network performance in terms of bandwidth blocking ratio as a function of the traffic load and the number of links upgraded from the C-band to the C+L bands. Moving towards other spectral bands provides more spectral resources, which leads to reductions in blocking probability. However, in the case of not having enough financial resources to achieve a fully upgraded network, the selection of fibers for migration must be done efficiently, for which the proposed ILP formulation is useful. The performance of the link upgrades provided by the ILP formulation is compared with a heuristic proposed in a previous work, by analyzing the reduction on the blocking probability obtained.