Optical ring metro networks with flexible Grid and distance-adaptive optical coherent transceivers

The utilization of distance-adaptive coherent optical transceivers in combination with a flexible finer-grained Wavelength Division Multiplexing (WDM) grid has been proposed in optical core networks to enable higher spectral efficiency and flexibility in the allocation of traffic flows. However, the application of distance-adaptive transceivers in metro networks, which are typically based on ring topologies and characterized by shorter distances and lower traffic volumes, is still an open research area both in terms of network resource savings and coherent technology requirements. This paper discusses and analyzes an optical metro ring network architecture with distance-adaptive coherent transceivers and formalizes the routing, modulation level, and spectrum assignment (RMLSA) optimization problem over such a network in order to evaluate the possible benefits introduced by the use of coherent technologies and of a spectrum grid of finer granularity in metro scenarios. Comparisons with legacy WDM systems show significant savings in terms of spectrum occupation and transceiver utilization.