scope:

This Recommendation specifies requirements for the optical transport network (OTN) long-reach interface OTU4-SC (completely standardized 100G optical transport unit order 4 for long-reach applications with staircase forward error correction (FEC)), which is intended for those OTU4-type applications that require a higher FEC coding gain than available from the [ITU-T G.709] FEC.

The OTU4-SC interface complements the existing functions specified in [ITU-T G.709], such as OTUk frame, ODUk/flex (where ODU is optical data unit), with a new hard-decision FEC codec, which uses the same overhead (OH) rate (~6.7%) as the OTU4 FEC codec.

This Recommendation makes use of existing [ITU-T G.709], [ITU-T G.798] and [b-ITU-T G-Sup. 58] functions by reference and it provides specifications for new functions that are specific to this new interface type. In addition, some introduction material for intended applications is included.