Patent ID: 7123404
Filing Date: 2006-10-17
Classification: H04B

Abstract:
1. An optical amplifier including a plurality of optical fibers doped with rare earth and a variable optical attenuator that are arranged on a transmission path of a light signal to be amplified, the light signal having a plurality of wavelengths, the optical amplifier comprising: an output unit configured to output a loss monitoring light having a wavelength that causes neither absorption nor gain with respect to each of the wavelengths of the light signal; a multiplexing unit configured to multiplex the loss monitoring light with the light signal at an input stage at which the light signal is input to be amplified into the optical amplifier; a demultiplexing unit configured to demultiplex multiplexed loss monitoring light from multiplexed light signal at an output stage at which amplified light signal is to be output from the optical amplifier; a detecting unit configured to detect intensity of the loss monitoring light at the time of multiplexing with the light signal and intensity of the loss monitoring light demultiplexed from the light signal; a calculating unit configured to calculate, based on the intensities, a loss of the loss monitoring light that has occurred between the input stage and the output stage; and a control unit configured to control, based on the loss, the variable optical attenuator so that an amplification gain for each wavelength of the light signal becomes flat.