| 摘要 |
PURPOSE:To detect a break point of an optical fiber quickly with high accuracy by detecting the break point based on a time difference when transmission signals with different wavelengths of at least two are intermitted and the group delay difference per unit length of the optical fiber in two wavelengths. CONSTITUTION:One end of two optical fibers 2Aa and 2Ab is connected to a time difference detector 5 via signal interruption detectors 4a, 4b at one terminal station. The group delay in each relay section is selected so that the group delay tauAn of the fiber 2Aa is larger than the other group delay tauBn of the fiber 2Ab without fail. If a fault takes place, the optical signal left in the left side fiber to the faulty point reaches one terminal station and then the signal is interrupted and detected by signal interruption detectors 4a, 4b. In this case, since the group delay of the fiber 2Aa and that of 2Ab differs, the time difference is detected by the time difference detector 5. Thus, the faulty point is detected quickly with high accuracy depending on the relation between the distance from the terminal station and the arrival time difference. |
