Filterless and Semi-Filterless Solutions in a Metro-HAUL Network Architecture

Filterless optical networks based on broadcast-and-select nodes have been proven to be a cost-effective alternative to active photonic network solutions in core networks. However, due to the emergence of novel metro-based high-bandwidth cloud-based services (e.g., Virtual Reality, 4K Video-on-Demand, etc.), filterless solutions have started to attract research attention also in the metro area. In this paper, we evaluate the performance of fully-filterless and semi-filterless (i.e., hybrid solutions between fully-filterless and active photonic architectures) optical-network architectures in terms of cost of network elements and spectrum utilization, in a metro-network scenario. Our evaluations show that, due to the ring-based hierarchical nature of metro networks, fully-filterless architectures tend to require excessive spectrum utilization as the broadcast effect spreads among all hierarchical rings. On the contrary, semi-filterless network architectures seem more promising due to the presence of filters that fend off the propagation of unfiltered channels. The results also show that it is more advantageous to deploy filters at nodes of the lower network levels than at nodes of higher network levels.