| 摘要 |
PURPOSE: To provide a simple and reliable line monitor system, with which sufficient information is applied for evaluating a fault point by making a monitor signal incident from a terminal to a fiber, returning it to the source terminal and evaluating the fault point from the amplitude and a delay time of loop back signal. CONSTITUTION: Line monitoring is performed by a passive loss loop-back circuit inside a repeater 12. An optical signal containing the monitor signal is sent from the terminal to an optical fiber 10 and connected through an optical amplifier 13 and a photocoupler 15 to an attenuator 16. The output of the attenuator 16 is connected to the input of a photocoupler 17 arranged at the output of an amplifier 14 of an optical fiber 11. The photocoupler 17 couples one part of lossed signal from the attenuator 16 with an input optical signal from the fiber 11 and returns it to the terminal that transmits a signal to the fiber 10. The monitor signal in that signal is extracted, and from its amplitude and delay time and the fault point evaluation is made. |
