ITU-T Recommendation G.973 is concerned primarily with the system performance and interface requirements of repeaterless optical fibre submarine cable systems. It considers both single wavelength systems (SWS) and wavelength division multiplexing systems (WDMS). It also covers the aspects related to the applications of discrete OFAs (power amplifiers, pre-amplifiers, remote optically pumped amplifiers) and/or distributed remotely pumped OFAs using Raman amplification.