OPTICAL FIBER AMPLIFIER

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PROBLEM TO BE SOLVED : To provide an optical fiber amplifier which is reduced in gain control error due to scattered light of a rare earth added fiber and holds a gain at a fixed value. SOLUTION : The optical fiber amplifier 100 according to an embodiment 1 reduces the influence of scattered light by adding an offset amount corresponding to input signal light power to a reference voltage used by a control circuit 109 for gain control. As the input signal light power increases, scattered light included in light passed through an optical filter 107 increases. Therefore, when such light is converted into a voltage to perform control so that the difference from the reference voltage becomes 0, since excitation light power becomes smaller than a value for imparting a desired gain, a plus offset corresponding to the increase of the input signal light power is added to the reference voltage. When the input signal light power decreases, on the other hand, a negative offset is only added to the contrary. COPYRIGHT : (C)2009, JPO&INPIT