| 摘要 |
PROBLEM TO BE SOLVED: To measure a line and a distance of fault points. SOLUTION: Each of optical fibers of a multiple branching optical path is made different in length (S1). A test light is inputted to the multiple branching optical path in an initial state without a fault, an OTDR (optical time region back scattering measurement method) waveform is measured from a time series change of the returning light, and event information composed of a distance and a level difference of Fresnel reflection points is obtained (S2). Fresh event information is obtained from the OTDR waveform for every constant time afterwards (S3) until a fault takes place (S5). The obtained two event informations are compared with each other and, the optical fiber in the initial state corresponding to the reflection points where distances do not agree is set as a fault line. Then, when the number of reflection points is smaller than in the initial state, a difference of the level differences of both event informations is obtained for each set of reflection points. A distance of the set of reflection points closest to the level difference of the reflection points present only in the initial state is set as a distance of the fault. On the other hand, when the number of the reflection points is equal, a distance of the reflection points not present in the initial state is set as the distance of the fault (S4). |
