| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical amplifier, which performs a control of a gain on the basis of the input power of signal light and can perform control of the gain, which realizes keeping of a constant gain with good accuracy, also in the case where the signal light wavelength distribution of multiple wavelength signal light is varied. SOLUTION: An excitation light power calculating part 21 provided in a gain control circuit 20 normally sets an excitation light power from an excitation light source 11, on the basis of an input power of signal light detected by a photodetector 22 to perform a constant control of a feed forward gain at high speed. At the same time, when the signal light is changed over and a variation is generated in the signal light wavelength distribution of multiple wavelength signal light, variation in the signal light wavelength distribution is detected by a wavelength distribution detecting means 30, and an excitation light power setting method in the calculating part 21 is modified on the basis of the result of the detection. Hereby, an optical amplifier, which always holds constant the gain with good accuracy, is obtained. |
