| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical amplifier capable of realizing a wider input dynamic range and low noises. SOLUTION: The optical amplifier has a wavelength-band division section dividing light from a transmission line into a plurality of bands, a plurality of the first optical amplifying sections changing the command of an optical amplifying output when the alteration of divided light set in response to each divided light reaches a fixed value, a plurality of attenuating sections attenuating outputs from a plurality of the first optical amplifying sections respectively, a plurality of the second optical amplifying sections amplifying outputs from a plurality of the attenuating sections respectively, a mixing section mixing outputs from a plurality of the second optical amplifying sections, and a plurality of control sections changing the quantity of the attenuation of a plurality of the attenuating sections, respectively. The control sections alter the quantity of the attenuation of the attenuating sections in response to the difference of the commands of optical amplifying outputs before and after the change when the commands of the optical amplifying outputs of the first optical amplifying sections are changed. Accordingly, the deterioration of a noise index can be inhibited without altering the output-light levels of the attenuating sections before and after the variation of input-light levels. |
