| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical amplifier alarm circuit with which the increase of natural discharge light outputted from an optical amplifier can be detected. SOLUTION: An optical signal 15 outputted from an optical amplifier 13 is branched into 1st-3rd optical signals 17, 19 and 22 by an optical brancher 16. The 1st optical signal 17 is outputted from an output side connector 18. The 2nd optical signal 19 is used for the control of amplification factor for fixing power. Concerning the 3rd optical signal 22, the wavelength component of main signal in the optical signal 12 is removed through an optical band pass filter 23, only the signal component of the other prescribed wavelength band is passed and that power is compared with a threshold value 37 by a comparator 37. As a result, when power exceeding the threshold value 37 is detected, the increase of natural discharge light is discriminated and an output abnormality alarm 38 is outputted. |
