METHOD OF APPLYING CHARACTERISTIC TO LIGHT AMPLIFIER AND CONTROLLING THE CHARACTERISTIC, AND LIGHT AMPLIFIER AND LIGHT AMPLIFIER KIT

PROBLEM TO BE SOLVED: To provide a method of applying characteristics to a light amplifier so that it may be operated at a specified again inclination and curvature within a set limit. SOLUTION: A test signal is transmitted to the light amplifier together with a pumping signal. Meanwhile, when the temperature of an erbium-added optical fiber 33 in the light amplifier changes, an output spectrum is sent to a computer 37 through an optical spectrum analyzer 35 to be compared with a desired spectrum. Under the condition that an input signal exists in an input port, different inclinations and curvatures measured at different temperatures are sent to an output port of the amplifier. The inclination and curvature measured at least one temperature out of a plurality of different temperatures is fed back to a heater 39 in the form of a feedback signal or information signal.