The present paper addresses future network architectures considered for Fixed Mobile Convergence, where users can access resources transparently either through fixed access technologies or through the mobile RAN. Optical technologies rely on Wavelength Division Multiplexing (WDM) to meet continuously growing bandwidth demands. However, although in the core network optical circuit switching may efficiently support huge traffic aggregates, closer to the access, in future Metropolitan Area Networks (MAN), it is necessary to provide a finer granularity, and a dynamical bandwidth control, to very heterogeneous traffic demands. This is supported by Optical Packet Switching (OPS) relying on WDM slotted Add/Drop Multiplexing (WSADM). A flow-based transfer mode, compatible with SDN control is first specified, and applied to bi-directional MAN rings. This mode is shown to provide several methods for supporting both local and global repair in case of failure. Mathematical models are derived to assess optical packet insertion performance and are used to illustrate how WSADM rings can support MAN performance requirements. Lastly the impact of locating the IP edge, and Data Centres closer to the users than in legacy architectures, within the MAN is addressed.