| 摘要 |
PURPOSE:To acquire communication state information at an optional location of an optical fiber line by converting part of an optical signal into an electric signal, counting the signal at a prescribed time interval, comparing the count with a number at a prescribed time interval at non-communication and discriminating it as the noncommunication state in case of coincidence and it as the communication state in case of dissidence. CONSTITUTION:A photodetector 12 is coupled optically to an optical fiber core-wire 11 in an optical fiber line, part of an optical signal is extracted and converted into an electric signal by the photodetector 12, either of the leading/trailing of a transmission signal at least is counted by a prescribed time interval and compared with a number at a prescribed time interval at known noncommunication state, and in case of coincidence, it is discriminated to be in the noncommunication state and to be in the communication state in case of dissidence. That is, the number of leading edges or of trailing edges or both counted at a prescribed time differ depending on noncommunication and communication state. Thus, the output of a counter 16 is discriminated by an arithmetic circuit 18 to discriminate whether it is a value at noncommunication or a value at communication thereby identifying whether the line is in the communication state or the noncommunication state. |
