| 摘要 |
PURPOSE:To secure speedily the safety of the human body in case of the breaking of an optical fiber by detecting reflected light which returns from a break point of an optical fiber to a light source side when the optical fiber is broken, and utilizing the detection output and turning off the light source. CONSTITUTION:If the optical fiber 5 is broken, transmitted light is reflected at the break point 6 to generate reflected light which travels in the opposite direction. The port C of an optical directional coupler 4 is coupled with a photodetector 7, which detects said reflected light and generates a detection signal output. This detection signal output is applied to a switch 2, which then turns off, thereby cutting off a driving current output supplied from a laser driving circuit 1 to a laser diode 3. |
