Recommendation ITU-T G.9804.3 describes a 50-Gigabit-capable passive optical network (50G-PON) system in an optical access network for residential, business, mobile backhaul and other applications. This system operates over a point-to-multipoint optical access infrastructure at the nominal line rate of 50 Gbit/s in the downstream direction. In the upstream direction, 12.5Gbit/s and 25 Gbit/s nominal line rates are defined currently, 50Gbit/s nominal line rate is for future study. This Recommendation contains the references, the common definitions, acronyms, abbreviations and the specifications of the physical media dependent layer of the 50G-PON system.