PURPOSE: To evaluate a length-wise fluctuation of a wave guide parameter, by extracting and detecting a back Rayleigh scattered waveform with respect to length-wise positions of an optical fiber to measure a Brillouin gain distribution for the light detected.
CONSTITUTION: Light from an inspection light source 1 brings a back Rayleigh scattered light from an optical fiber 13 to perform a photo and photoheterodyne detection of a local oscillation laser 18 with a photo detector 19. Here, a portion along of the back Rayleigh scattered light waveform corresponding to a desired optical fiber length-wise position is extracted with a waveform shaping optical element 14 to detect light. Thus, an output from the photo detector 19 is inputted into a lock-in amplifier 24 as input thereinto 24 while a signal from a modulator 6 done so as reference signal thereby enabling the outputting of a Brillouin gain distribution with respect to a noted position along the length of the optical fiber as function of a sweep light frequency of an inspection light source 1 being swept with an oscillator 2.
TATSUTA MITSUHIRO
KATSUYAMA YUTAKA
