| 摘要 |
PURPOSE:To search for a fault point without stopping the use of a circuit by monitoring clocks in two optical fiber cables for transmitting light signals in the opposite directions, and changing the transmission directions at a detecting station when a fault occurs. CONSTITUTION:A master station 0 and subordinate stations 1-(m) are connected in series through optical fiber cables A1-An forming a closed loop and optical fiber cables B1-Bn which have receiving terminal opened at the master station 0 and do not form a closed loop. Light signals containing clocks are transmitted from the master station 0 through the transmission lines A1-An, and B1 and Bn in the opposite directions, and each station monitor the clock signals invariably. If a fault occurs to a subordinate station or transmission line, an adjacent station detects the fault from the clock signals to switch the transmission line to the other transmission line in the opposite direction, thereby transmitting transmission information which contains additional fault information without containing the clock to the master station. The master station receives the fault information to give display warning of the fault, and connects the transmission lines B1 and B2 together to send a signal to them. The fault detecting station switches the transmission lines and sends the received signal back to the original transmission line. |
