Abstract: A branching unit for an optical fibre cable system of the type which has an electrical power conductor for feeding current to electrical equipment provided along a main cable and a communication system and method of operating such a system is disclosed. The branching unit (10) has first and second connections (12, 14) for coupling two sections of trunk cable (16, 18) and a third connection (24) for an optical fibre spur cable (26). A switch arrangement (RL1, RL2, D9, D10) is provided on the conductor of the spur cable (26) to apply an earth (36) to the conductor of the trunk cable (16, 18). This maintains a current path in one trunk section when a failure or break occurs in the other trunk section.

Abstract: A wavelength division multiplex branching unit for an optical fibre transmission network comprises a branching unit housing (100) and means (102) external to the housing for permitting the connection of one or more wavelength selective devices (A, B, C, D) to a trunk transmission fibre. The wavelength selective devices are each responsive to a different transmission wavelength and are effective to direct transmission signals have that response wavelength from the trunk fibre to a spur fibre of the branch cable.