DUPLICATED NODE EQUIPMENT

PURPOSE:To normally operate a loop by adopting the constitution that an optical branching device and a demultiplexer are inserted so as to duplicate two node equipments completely and switching the system to the other standby system even if the optical transmission/reception section causes a fault. CONSTITUTION:The titled equipment consists of the optical branching device 9 and the demultiplexer 10. An optical signal inputted from a loop optical fiber transmission line 1 is divided into two by the optical branching device 9 the one signal is given to an optical receiver 2 of the node 8A and the other is inputted to the optical receiver 2 of the node equipment 8B, the signals are converted into an electric signal and given to a transmission controller 4. A changeover control section 5 supervises the state of both the equipments 8A, 8B, controls that one equipment is used as an active equipment and the other is used as a standby equipment and controls the changeover section 6 so that the connection of the terminal equipment or the like is executed to the active side at the same time. Even if the optical transmission/reception section causes a fault, the loop is operated normally by switching the system to the standby system.