This Recommendation describes the transmission convergence layer for 10-Gigabit-capable passive optical network (XG-PON) systems – a family of flexible access network systems that operate over a point-to-multipoint optical access infrastructure at the nominal data rate of 10.0 Gbit/s in at least the downstream direction, while providing a wide range of broadband and narrow-band services to end-users.

This Recommendation specifies:

– the layered structure of the XG-PON transmission convergence (XGTC) layer;

– functionality of the service adaptation sublayer, including XG-PON encapsulation method (XGEM), XGEM frame delineation, and service data unit (SDU) fragmentation;

– functionality of the framing sublayer with the specification of the downstream XG-PON frame and upstream burst formats;

– functionality of the physical interface (PHY) adaptation sublayer, including forward error correction and scrambling;

– XG-PON embedded management functionality, including upstream time-division multiple access and dynamic bandwidth assignment mechanisms;

– the XG-PON physical layer operation, administration and management (OAM) messaging channel;

– the optical network unit (ONU) activation method;

– timing aspects of point-to-multipoint operation and time-of-day communication;

– cryptographic mechanisms for authentication, integrity verification, channel isolation and data protection along with and the associated key exchange protocols;

– signalling mechanisms and protocols to support ONU power saving.

This Recommendation forms an integral part of the ITU-T G.987 series of ITU-T Recommendations [ITU-T G.987], [ITU-T G.987.1], [ITU-T G.987.2] that, together with [ITU-T G.988], specify a single coherent set of access transmission systems.