| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical fiber amplifier where an output signal light intensity is constant and a gain spectrum does not fluctuate, even if an input signal light intensity fluctuates when a small number of photodetectors is used. SOLUTION: Signal light is amplified by an Al-doped EDF(erbium-doped fiber) 30 where excitation light outputted from a laser light source 32 for excitation is supplied, is attenuated by a variable light attenuator 40, and is amplified by a P/Al-doped EDF 50 and Al-doped EDF 51 where excitation light outputted from a laser light source 52 for excitation is supplied. An insertion loss due to the variable light atteneuator 40 is controlled by an insertion loss control circuit 70 from an input signal light intensity detected by an input signal photodetector 21 and the gain deviation of the optical fiber amplifier is maintained to a minimum. The intensity of exciting light outputted from the laser light source 52 for excitation is controlled by an excitation light control circuit 71 from an output signal light intensity detected by an output signal light detector 61, and the output signal light intensity of an optical fiber amplifier is maintained constant. |
