| 摘要 |
PROBLEM TO BE SOLVED: To prevent accumulation of output fluctuation of many optical fiber amplifiers even when amplifiers are connected in series by controlling the stimulating light so that the difference between output signal light and a target value becomes smaller by using the sample data held by means of a sample-hold circuit as the target value, and comparing the target value with the output signal light detected by means of an optical light monitor. SOLUTION: A sample-hold value is inputted to a comparator 13 as a new target value and compared with an output signal light 6 detected by means of an output light monitor 9, and the stimulating light of a semiconductor laser 8 for excitation is controlled, in accordance with an error signal obtained based on the comparison. Since a signal level detecting circuit 11 and a sample-hold circuit 12 are always operated and the target value is updated whenever variations of the signal level is detected, the output signal light 6 changes in stages according to an input signal light 1. In a sample-held state, the output signal light becomes constant, regardless of the state of the input signal 1 and it is possible to prevent the accumulation of the output variations regardless of the number of optical fiber amplifiers even when the amplifiers are connected in series. |
