This Recommendation addresses optical fibre maintenance support, monitoring and testing systems for trunk optical fibre cable networks. It describes fundamental requirements, functions and test procedures for use in maintenance operations. It applies to the test equipment and methods, configuration and optical devices, such as test access devices for connecting the test equipment to the communication line, which are components of the maintenance system.

The aspects related to active monitoring to detect communication signal degradation and the status of the transmission equipment are described in [ITU-T G.697]. The functional architecture and parameters specialized for submarine applications are described in [ITU-T G.979].