Recommendation ITU-T G.709.2/Y.1331.2 defines the requirements for the optical transport network (OTN) long reach interface OTU4-SC@ 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@ with a new hard-decision FEC codec@ which uses the same overhead rate (-6.7 %) as the OTU4 FEC codec. This Recommendation makes use of existing [ITU-T G.709]@ [ITU-T G.798] and [ITU-T G.Sup58] 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.