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Optical metro networks evolution driven by 5G requirements face enormous challenges. Network functions virtualized in the data centers spread to the metro nodes, IP, and optical technologies must cooperate to meet the metro traffic aggregation role. Multiple technological options exist, and carriers confront the need to economically assess them, benchmarked in realistic deployments. This paper gives relevant insights to this aim. We first construct a set of metro network benchmarks. A strategic and distinctive effort is made to incorporate metro WDM topologies, traffic profiles and daily variation patterns, fault-tolerance requisites, and network operational choices, that faithfully reflect the expected 5G metro progression for a national carrier. Then, we use these networks to assess two technological choices. On one hand, the cost-effectiveness limits in terms of CAPEX reductions and energy efficiency brought from the possibility of having an agile control plane in the metro, capable of on-demand instantiation of IT and network resources. On the other hand, we investigate the benefits of replacing ROADMs by more cost-effective filterless technologies, but just limiting this replacement to degree-1 and degree-2 optical nodes, that are prevalent (e.g. >50%) in regional metro topologies. A novel capacity planning algorithm has been developed for IT, IP and optical resources allocation and dimensioning, providing fault-tolerant designs for the realistic scenarios defined. Simulation results have been obtained using the Net2Plan NIW (NFV over IP over WDM) open-source framework. Developed algorithms and part of the testing scenarios are available for inspection in public repositories of the EU METRO-HAUL project, the umbrella for our work. Our results show CAPEX benefits in the order of 10% and energy savings in the order of 20-30% stemming from the on-demand resource allocation in the metro. In addition, degree 1 and degree 2 optical nodes have shown to be a sweet spot for applying filterless switching, with mitigated impact of the associated spectrum waste.

This paper presents the high-level COCONUT architecture of an optical access network based on coherent technology, supporting ultra-dense Wavelength Division Multiplexing (WDM). The COCONUT network should allow for seamless evolution from present PON architectures, but also support new emerging applications such as mobile back-haul and front-haul. Coherent techniques will hence allow serving a higher number of users, thanks to ultra-dense WDM, and reaching higher power budget, thanks to higher sensitivity. These features should allow for economy of scale and network consolidation. Although coherent solutions are well-developed for core networks, the prohibitive cost of their optical and electronic parts makes them unsuitable for the massive deployment of access networks. To this aim, COCONUT will address realization of coherent transmitter/receivers exploiting low-cost components and simple electronics, so that the cost of typical line terminals would be affordable to the end-users. The paper presents an overview of the target results and key issues that are addressed by the COCONUT partners.