ITU-T Recommendations

Recommendation ITU-T G.989.3 specifies the transmission convergence layer of 40 Gigabit-capable passive optical network (NG-PON2) systems providing optical access for residential, business, mobile backhaul and other applications.
An NG-PON2 system supports multiple wavelength channels and enables flexibility to add capacity as the demand grows to 100 Gbit/s and beyond. An NG-PON2 system may contain a set of time and wavelength division multiplexing (TWDM) channels, or a set of point-to-point wavelength division multiplexing (PtP WDM) channels, or both. The TWDM channels operate at the nominal line rates of 9.95328 and 2.48832 Gbit/s in both downstream and upstream directions. The PtP WDM channels support nominal line rate classes of 1.25 Gbit/s, 2.5 Gbit/s and 10 Gbit/s, depending on the PtP WDM client.
The transmission convergence (TC) layer is the protocol layer of the NG-PON2 system that is positioned between the physical media dependent (PMD) layer and service clients. It builds on Recommendation ITUT G.987.3, with modifications for NG-PON2 specific features.
This Recommendation forms an integral part of the ITU-T G.989 series of Recommendations (ITUT G.989, ITU-T G.989.1 and ITU-T G.989.2) that, together with the ONU management and control interface (OMCI) Recommendation, ITU-T G.988, specifies a coherent set of access transmission systems. The NG-PON2 system is also a member of the ITU-T G.9802 family.
Amendment 1 to ITU-T Recommendation G.989.3 Rev 2 (2021) incorporates regular maintenance items, supplying new Appendix XI describing the behavior of an NG-PON2 ONU in the Emergency Stop state, introducing the deactivation reason code reported downstream for offline troubleshooting purposes, and fixing the inconsistency in handling of the Forgotten ONU timer TO6.