A WDM mesh network offers great flexibility in dynamically re-configuring the optical core to match the IP layer demands. WDM networks provide high bandwidth, on the order of tens of Gigabits per second per channel. With Dense WDM (DWDM), an aggregate of several Terabits per second rates are achievable. Longer reach, higher scalability and simpler integration with radio access are features that are also pursued. The first architecture presented employs both the optical and the electrical domains by means of combined TDM and WDM multiplexing, inherited from transport networks, in a metro/access topology, the second makes intensive use of the electrical frequency multiplexing (OFDM) over the fiber and the third makes exploits the wavelength multiplexing, with very narrow channel spacing (ultra-dense-WDM).