Patent ID: 6738185
Filing Date: 2004-05-18
Classification: H01S,H04B

Abstract:
An optical amplifier comprising:an optical amplifier medium; a pumping light source for supplying pumping light of a predetermined wavelength to said optical amplifier medium; a first coupler for separating part of signal light to be inputted to said optical amplifier medium; a second coupler provided so as to sandwich said optical amplifier medium together with said first coupler, said second coupler separating part of the signal light amplified in said optical amplifier medium; and a gain control circuit for controlling a gain of said optical amplifier by use of information concerning power of the light respectively separated by said first and second couplers, wherein said gain control circuit includes: a first photodetector for outputting a voltage having a linear relation with the power of the light separated by said first coupler; a second photodetector for outputting a voltage having a linear relation with the power of the light separated by said second coupler; a comparator for outputting a difference voltage between the voltages respectively outputted from said first and second photodetectors; and a drive circuit for supplying a desired drive current to said pumping light source in response to the voltage outputted from said comparator, and wherein said gain control circuit has a structure for performing gain control by adjusting an inclination a and an intercept b in a function (Vo=aÂ·Pi+b) for defining the linear relation between inputted optical power Pi and an outputted voltage Vo concerning said first and second photodetectors.