| 摘要 |
PURPOSE:To enable live-line contrasting without affecting currently used communications by projecting test light of a wavelength different from the wavelength of the currently used light to a live-line optical fiber, allowing the test light to leak from the detecting part of the live-line optical fiber and detecting the same. CONSTITUTION:The test light from a test light source 5 is projected from an optical coupler 4 to the live-line optical fiber 1 and the detecting part 7 of the live-line optical fiber 1 is bent to allow the test light to leak to the outside of the live-line optical fiber 1 at the time of contrasting the live-line optical fiber 1. The leaking test light is detected by means of a detector 8 and is checked by the detector 8 that said light is in the same optical path (optical fiber). The contrasting is thus executed. The currently used light under transmission in the live-line optical fiber 1 at this time transmits an optical filter 6 but the remaining test light under transmission in the fiber 1 is reflected by the optical filter 6 and is radiated to the outside of the fiber 1. The test light is, therefore, not projected to a photo/electric converter 3 of the fiber 1 so that no influences are exerted to the currently used communications.
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