| 摘要 |
PROBLEM TO BE SOLVED: To make constant the signal intensity of a signal light which is different in signal intensity. SOLUTION: A semiconductor optical amplifier 101 amplifies the signal light S with an amplification factor, corresponding to an injected current I and outputs an amplified signal light So. A continuous light P is also inputted to the semiconductor optical amplifier 101, and the continuous light P is processed by mutual gain amplification with the signal light S, becoming mutually gain- modulated light Po. The light intensity of the mutually gain-modulated light Po is small, when the signal light intensity of the signal light S is large and is large, when the intensity is small. Only the light frequency components of the continuous light in the mutually gain-modulated light Po passes through a wavelength filter 106 and are received by a photodetector 107. The photodetector 107 outputs a light-intensity detection signal K, corresponding to the quantity of the photodetection. A control circuit 105 makes the injected current I large, when the light intensity detection signal K is large and is small, when the signal is small. Consequently, the signal intensity of the signal light So becomes constant. |
