LIGHT AMPLIFIER AND CONTROL METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To control an output signal light constant even though the deterioration of optical parts or the like are generated in a bi-directional exiting. SOLUTION: A driving current with respect to the light source of a front exciting light is controlled by a front side control circuit 12 and the driving current with respect to the light source of a rear exiting light is controlled by an output control circuit 22 based on the quantity of an output light and when the driving current of with respect to the light source of the rear exciting light exceeds a fixed value, changeovers are performed by a first changeover unit 14 and a second changeover unit 24 so as to control the quantity of the output light by the driving current with respect to the light source of the front exciting light.