Optimization of spectrally and spatially flexible optical networks with spatial mode conversion

Spectrally and spatially flexible optical networks (SS-FONs), which combine space division multiplexing (SDM) with flexible-grid elastic optical network (EON) technologies, bring additional complexity to network control due to the handling of a larger number of spatial modes in SDM than in conventional EONs. To effectively optimize such networks, in particular, to generate good-quality solutions of low optimality gaps in reasonable computation times, efficient algorithms are required. In this work, we focus on the routing, spatial mode, and spectrum allocation (RSSA) problem in the SS-FONs in which conversion of spatial modes in switching nodes is allowed. We propose and evaluate two enhancements in RSSA processing, namely, algorithm parallelization and application of dedicated data structures, which are built into a hybrid simulated annealing with greedy RSSA heuristic algorithm. To assess the quality of generated RSSA solutions, we develop suitable procedures for estimating solution lower bounds. The results of numerical experiments show the effectiveness of proposed techniques in speeding up the search for good-quality RSSA solutions.