Ultra Dense Wavelength Division Multiplexing (UDWDM) has been proposed for future Passive Optical Networks (PONs) to support the increase of access traffic, furnishing an improved capacity while introducing point-to-point logical connections with the Wavelength-To-The-User (WTTU) concept, enabled by low cost coherent transceivers with high sensitivity. Furthermore, considering wireless networks, a centralized processing in a Cloud-Radio Access Network (C-RAN) needs reconfigurable abilities to bring benefits to mobile systems with dynamic demands of huge bandwidth between Remote Radio Heads (RRHs) at base stations and Baseband Units (BBUs) at the central office. To achieve this goal in the access network, we propose a flexible architecture design of an UDWDM-PON, which adapts the available bandwidth to different users and classes of services and can reconfigure the connections between RRHs and BBUs. © 2018 IEEE.