| 摘要 |
PURPOSE:To attain measurement of the backscattering light generated in an optical waveguide in a high signal-to-noise ratio by providing an electrostrictive vibrator, an AC oscillator and a lock-in amplifier. CONSTITUTION:The output light of a light source 1 is collimated by a lens 2 and becomes parallel beams, and split into two by a beam splitter 3. One of the split light beams is made incident on an optical waveguide 5 to be measured through a lens 4. The other of the split light beams is brought to total reflection 6 and made incident on the splitter 3 again, and multiplexed with a backscattering light generated in the waveguide 5. This multiplexed light is made incident on a photodetector 8. Subsequently, an electrostrictive vibrator 12 is driven by a sine wave from an AC oscillator 13, and brings the reflecting mirror 6 to minute vibration in the direction of an incident beam. In such a manner, a reflected light of the reflecting mirror 6 is brought to phase modulation. At this time, the output of the detector 8 is derived, a frequency (f) component and a frequency 2f component are detected by lock-in amplifiers 14, 15, respectively, and they are brought to A/D conversion 16, 17 and supplied to a signal processing part 11. |
