OPTICAL AMPLIFIER

PROBLEM TO BE SOLVED: To provide a low-cost WDM optical amplifier that can maintain a flat predetermined signal light output level and output wavelength characteristic for a variation in signal light input level through simple control, allowing a wide input dynamic range. SOLUTION: The optical amplifier has a variable optical attenuator 21 between a former optical amplifier 11 and a latter optical amplifier 12, and also has a variable optical attenuator 22 at the output side of the latter optical amplifier 12, and if the signal light input level of a WDM light inputted into the input port IN is lower than the base point level, control is done such that the attenuation amount of the variable optical attenuator 21 in-between is not increased (basically kept to a minimum), and the attenuation amount of the variable optical attenuator 22 at the output side is increased just by a portion by which the signal light input level is increased. On the other hand, if the signal light input level is higher than the base point level, the attenuation amounts of both variable optical attenuators 21 and 22 in-between and at the output side are controlled in accordance with the signal light input level. COPYRIGHT: (C)2007,JPO&INPIT