Apparatus for detecting a fault location in an optical fiber line

摘要

Disposing optical fiber gratings 10a each reflecting a wavelength &lgr;1 which is different from a signal wavelength &lgr;s along an optical fiber line 10 at suitable intervals and positions. The wavelength &lgr;s of signal light is not reflected by the grating 10a, but transmitted through the optical fiber line 10. An optical pulse tester 14 outputs probe pulse lights of wavelengths &lgr;0, &lgr;1, which are different from the signal wavelength &lgr;s, at slightly different times. The probe lights of the wavelengths &lgr;0, &lgr;1 are input into the optical fiber line 10 through an optical adding and dividing device 16 and transmitted through the optical fiber line 10. Reflected light of the wavelength &lgr;1 of probe light contains therein reflection pulses of the grating 10a, and each reflection pulse serves as a position reference. The probe light of the wavelength &lgr;0 does not contain reflection light of the grating 10a. Comparison of the reflected lights of the wavelengths &lgr;0, &lgr;1 to each other by the optical pulse tester 14, provides determination of whether there is a fault location, and, if so, detection of fault location with high precision can be made.