This Recommendation describes the Forward Error Correction (FEC) functions that have higher-correction ability than RS(255,239) code defined in ITU-T Rec.G.975 in the optical fibre submarine cable systems. This Recommendation alsodescribes the system requirement concerning supervision for the submarine cable systems. The applications being addressed in this Recommendation are both optically amplified repeatered systems (ITU-T Rec. G.977) and repeaterless optical systems (ITU-T Rec. G.973). The use of this FEC function in submarine terminal transmission equipments (TTEs) should not be considered as mandatory.