"The purpose of this Recommendation is to provide optical interface specifications towards the realization of transversely compatible dense wavelength division multiplexing (DWDM) systems intended for repeaterless submarine applications. This Recommendation defines parameters for single-channel optical interface of physical point-topoint DWDM applications on single-mode optical fibres through the use of the ""black-link"" approach. Applications containing DWDM optical amplifiers are not defined in this Recommendation. This Recommendation describes DWDM systems that include the following features: ?C Channel frequency spacing: 100 GHz and below (defined in [ITU-T G.694.1]). ?C Bit-rate of signal channel: up to 10 Gbit/s."