Recommendation ITU-T G.971 applies to optical fibre submarine cable systems. The purpose of this Recommendation is to identify the main features of optical fibre submarine cable systems, and to provide generic information on relevant Recommendations in the field of optical fibre submarine cable systems. A common implementation relevant to all the optical fibre submarine cable systems is described in Annex A. Specific information relevant to each optical fibre submarine cable systems is included in annexes of other Recommendations. The updated data on cable ships and submersible equipment of various countries are also described in Appendix I. In this latest version, the diagram of interoperable optical fibre submarine cable systems and boundaries are described in Fig.1 (b).