| 摘要 |
PROBLEM TO BE SOLVED: To achieve high-resolution measurement on the characteristics such as loss distribution, of a reception system, even if the reception system is of a narrow band, by preventing the band widening of the reception system determined by a pulse width. SOLUTION: A laser beam caused to enter an optical transmission path is bifurcated by an optical coupler 4-1. Laser beams acquired by the bifurcation are severally pulse-modulated by intensity modulators 3-1 and 3-2. One of the pulse-modulated pulse beams is caused to enter a measured optical fiber 7 as a test beam. A back-scattering beam from the fiber 7 is guided out by means of an optical coupler 4-2. The other pulse-modulated pulse beam is coherent-detected by being combined as a reference beam with the back-scattering beam from the fiber 7 at an optical coupler 4-3. A signal thus detected is used to find an OTDR waveform by sampling. On this occasion, the cycle of pulses of the reference beam is set so that beam pulses are shifted from each other by an integer fraction of time of a beam pulse to go to and return from the fiber 7. COPYRIGHT: (C)2011,JPO&INPIT |
