| 摘要 |
PURPOSE:To perform an easy detection of a near-end breaking point, by preventing saturation of an amplifier by dint of a reflecting light from a photo connector and a back scattering light. CONSTITUTION:A laser pulse light from a laser device 13 is caused to enter an optical fiber 16 to be measured via a photo coupler 14 and a photo connector 15, and a reflecting pulse light by a breaking point 17 and a reflecting light by a back scattering are separated by the photo coupler 14 to apply it to a photo switch 20. A signal from a function generator 21, delayed by a delay circuit 22, is applied to the photo switch 20 to control a quantity of light applied to a photo detector 18. The photo switch 20 acts as a photo attenuator which varies with a reflecting light from a near-end part with the passage of time, and this prevents the occurrence of saturation at an amplifier 19 and enables accurate amplifying of also a detecting signal of a reflecting pulse light from a near- end breaking point. |
