OTDR where the dichotomize it does the laser light which incidence is done in light ray path reflected distribution

摘要

PROBLEM TO BE SOLVED: To measure reflection distribution in a fiber with distance resolution of 1 cm or less while compensating the effect of wavelength dispersion of a measured optical path.;SOLUTION: An incident laser beam is branched into two. Branched laser beams are pulse-modulated by intensity modulators 3-1 and 3-2, respectively, one for a test beam and the other for a reference beam. The test beam is caused to enter a measured optical fiber 7. A reflective beam from the fiber 7 is guided out and combined with the reference beam. An obtained beam is received/demodulated by a light receiver 5 to find an OTDR waveform through sampling by means of an AD converter 6. The OTDR waveform is analyzed by an analyzer 8 to measure reflection distribution. Through a controller 9, pulse generating time is controlled by the analyzer 8 to lower the band of the reflective beam from the fiber 7 to the frequency of a pulse train of the reference beam. The measurement of a reflection position is repeated while displacing times at which the reflective beams are combined with reference beam pulses for each of test beam pulses by displacing the cycle of the pulse train of the reference beam from the frequency of the send-out cycle of test light pulses to determine a position where reflection exists from displacement of the reflection position.;COPYRIGHT: (C)2011,JPO&INPIT