| 摘要 |
PURPOSE:To improve the reliability of the light amplifier by detecting the light quantity of an optical signal outputted from the final element out of plural semiconductor laser type light amplifying elements vertically arranged on the optical path of the optical signal and selectively adjusting a current quantity to be supplied to each of plural elements based upon the detected light quantity. CONSTITUTION:An optical signal attenuated through a transmission line is projected from an input fiber 1, condensed by a lens 2, injected into the 1st semiconductor laser element 3 forming reflection preventing films on both the end faces and acting as a light amplifier, condensed by a lens 4, and then injected into the 2nd semiconductor laser element 5 forming reflection preventing films on both the end faces and acting as a light amplifier. The deterioration of the current light amplifier element 3 is sensed by monitoring the quantity of output light and the current element 3 is automatically switched to the spare light amplifier element 5 to use the spare 5 in accordance with a change in the quantity of current supplied to the current element 3. Thus, the reliability of the amplifier can be improved. |
