| 摘要 |
PURPOSE:To effectively use signal optical power, by controlling the gain of an optical amplifier, on the basis of spontaneous radiation light generated in the optical amplifier. CONSTITUTION:Optical power of a wavelength which is in the gain bandwidth of an optical amplifier 1 and different from the amplication signal light wavelength is detected with an optical branching filter 2 and a photo detector 3. At this time, the spontaneous radiation light power of the optical amplifier 1 is detected, which power is changed by the excited state of the amplifier 1. The spontaneous radiation light power is large in the high excited state and becomes small in the low excited state. Control is performed in the following manner; when the spontaneous radiation light power is smaller than a specified d value, the excited state is increased, and when the power is large, the excited state is decresed. Thereby the spontaneous radiation light power can be kept constant. The spontaneous radiation light power is in the one-to-one relation to the signal gain of the optical amplifier 1, so that the signal gain is kept constant by keeping the spontaneous radiation light power constant. Thereby the signal light power can be effectively used. |
