Routing and wavelength assignment problems in optical networks—comparing formulations for solution by quantum annealing

We develop four different quadratic unconstrained binary optimization formulations of routing problems relevant to the optical transport layers in telecommunications networks. Our formulations handle joint routing and wavelength assignment, unicast, multicast trees, and shared risk avoidance. We show that this approach is viable, even for multicast, and we test and compare the effectiveness of each formulation at solving these problems using the DWave hybrid solver. We describe expedients we applied to ensure valid solutions, along with challenges of the QUBO approach.