| 摘要 |
PURPOSE:To attain the detection of a disconnected optical fiber, by reflecting an optical signal of an optical transmitter of a central processing unit on a mirror at a terminal controller side and returning the signal to an optical receiver. CONSTITUTION:The optical signal of a light emitting diode 111 is made incident to an optical branching device 50 via an optical branching device 40 and an optical fiber 30 and branched into two. One is reflected on a mirror surface 100 and the other is outputted from the aperture. The optical signal reflected on the mirror surface returns to the fiber 30, is branched at the branching device 40 and a part of the branched signal is made incident to a photodiode 121. The returned optical signal is amplified at an amplifier 122 and inputted to the central processing unit 10. If the fiber 30 is disconnected in the process above, the optical signal does not reach the mirror surface 100 and the returned light from the reflection is not incident to the photodiode 121. The presence of open optical fiber is detected by taking notice to an output signal of the amplifier 122. |
