EVALUATING DEVICE FOR CHARACTERISTIC OF BRANCH LIGHT BEAM PATH

摘要

PURPOSE:To evaluate the characteristics of a downstream-side optical fiber from the waveform difference between the time waveform of light emitted by a signal light source and a pump light source and the time waveform of light from only the signal light source. CONSTITUTION:The pulse light from the signal light source 8 is sent to the downstream-side optical fiber 4 to generate backward Rayleigh scattered light and Fresnel reflected light. Those light beams travel backward from the optical fiber 4 to the light source 8 and the time waveforms of those light beams are recorded on a waveform processor 14. Then CW light from the pump light source 9 is sent to the optical fiber 4 and the current frequency of the light source 9 is brought under frequency control 13 to equalize the difference from the frequency of the light source 8 to the frequency of the acoustic wave of one specific optical fibers among optical fibers 4. Consequently, only one specific optical fiber enters a preamble amplification state and the backward Rayleigh scattered light and Fresnel reflected light travel backward to the light source 8. The time waveform of this light is recorded on the device 14, which finds the waveform difference between the time waveform of the light obtained when the light sources 8 and 9 are used and the time waveform of the light obtained when only the light source 8 is used. The characteristics of the specific optical fiber 4 can be evaluated from the waveform difference.