OPTICAL AMPLIFIER

PROBLEM TO BE SOLVED: To provide an optical amplifier which is easy to be controlled as a plurality of amplifiers are connected in multiple stages. SOLUTION: Input signal optical power is monitored by an optical coupler 11 and a light receiving element 61. Output signal optical power is monitored by an optical coupler 12 and a light receiving element 62. The number of waves of signal light is monitored by a wave number information monitoring part 90. A control unit 811adjusts the power of excited light outputted from an excitation light source 71 and an excitation light source 72 based on the result of input signal light power monitoring, the result of output signal light power monitoring, and the result of wave number information monitoring, to control the entire gain of an optical amplifier 1 to be constant. A control unit 821adjusts the loss of signal light in a variable optical attenuator 40 based on the result of input signal optical power monitoring and the result of wave number information monitoring, to control the output signal optical power to be constant. COPYRIGHT: (C)2006,JPO&NCIPI