| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical amplifier that has an autonomous control function for making the gain flat. SOLUTION: The optical amplifier includes an optical amplifier section 1 for directly amplifying signal light with a plurality of wavelengths, a laser diode 2 for generating auxiliary signal light with a wavelength shorter than the wavelength range of the main signal with one or more wavelengths within a prescribed wavelength range and modulated with a frequency f1, a laser diode 3 for generating auxiliary signal light with a wavelength longer than the wavelength range of the main signal and modulated with a frequency f2, a 13 dB photocoupler 7 for composing the main signal light with the two pieces of auxiliary signal light and outputting the result to the optical amplifier section 1, electric filters 11, 12 for separating the two pieces of auxiliary signal light with modulation signals having the frequencies f1 and f2 to detect them, a control circuit 13 for controlling the gain of the optical amplifier section 1 according to the respective modulation signal levels detected by the electric filters 11, 12, and an optical filter 9 for outputting only the main signal light included in the output light of the optical amplifier section 1 as the amplified light to the outside. |
