ITU-T Y.1331.4 PDF

This Recommendation specifies 25 Gbit/s and 50 Gbit/s optical transport network (OTN) short-reach interfaces with Reed-Solomon forward error correction codes (OTU25-RS, OTU50-RS) with lower overhead percentage than the Reed-Solomon forward error correction (FEC) code specified for OTUk (k=1,2,3,4) in [ITU-T G.709].

The OTU25-RS and OTU50-RS interfaces complement the OTU25/ODU25 and OTU50/ODU50 functions specified in [ITU-T G.709], with a hard-decision FEC codec, which uses the same overhead percentage (~5.8%) as the FlexO-x-RS FEC codec.

The OTU25-RS and OTU50-RS interfaces may be operated at an approximately 8% and 5% lower rate for use in network scenarios that do not require the support of all clients. Such interfaces are identified as OTU25u-RS and OTU50u-RS interfaces. The OTU25u-RS interface will be equipped with a hard-decision FEC code, which uses a ~3% lower overhead percentage.

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.