| 摘要 |
PROBLEM TO BE SOLVED: To provide a light fiber amplifier capable of performing a constant gain control even though lateral natural emitted light from amplifying light fiber or residual exciting light cannot be emitted. SOLUTION: A light connector 111, monitor coupler 121, light isolator 131, WDM coupler 141, erbium doped fiber(EDF) 151 to 153, WDM coupler 142, light isolator 132, monitor coupler 122 and light connector 112 are longitudinally connected in the order as listed above from the input end to output end of signal light. A control circuit 170 controls the intensity of exciting light constant which is supplied to EDF151 to 153 in forward direction and also controls the intensity of exciting light supplied from backward direction to EDF151 to 153 through WDM coupler 142 in such a manner that the gain determined from a ratio between output signal light intensity and input signal light intensity detected from photodiodes 161 and 162 can be kept constant. |
