| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical amplifier which can be controlled stably even when the wave number of input signal light is changed and to provide an optical transmission system which restrains a transient gain change in the optical amplifier and which restrains the degradation of a transmission characteristic even when the wave number of the signal light to be input to the optical amplifier is changed due to the generation of a trouble or due to the action of a signal-light branching and insertion means. SOLUTION: The greater part of the input signal light is optically amplified in an optical amplification medium 13 via a first optical divider 12a. The greater part of the optically amplified signal light is output to the outside via a second optical divider 12b. A part of the input signal light is branched by the divider 12a, it is delayed by the delay time Δt by using a delay medium 14, it is received by a first photodetector 15a, and an input signal light intensity Pin is detected. A part of the optically amplified signal light is branched by the divider 12b, it is received by a second photodetector 15b, and an output signal light intensity Pout is detected. By a control part 17, the intensity of excitation light supplied to the medium 13 by an excitation light source 16 is adjusted on the basis of the intensity Pin at the time t-Δt and on the basis of the intensity Pout at the time t. |
