OPTICAL AMPLIFIER GAIN CONTROLLING APPARATUS AND METHOD

PROBLEM TO BE SOLVED: To automatically and dynamically control the gain deviation between wavelengths of an optical wavelength-multiple signal against the time variation by adaptively controlling the attenuations of lower-order diffracted lights at wavelengths to combine them, using an optical divider utilizing the diffraction effect of the light for dividing the wavelength-multiple signal into individual optical wavelength signals. SOLUTION: An optical wavelength-multiple signal 1 composed of wavelength- multipled optical signals at wavelengths λ1, λ2,..., λn is inputted to an optical wavelength-multiple signal dividing means 2 which divides it into individual optical wavelength signals and the most of them are inputted to an optical attenuating means 3. An optical attenuation control means 6 controls the optical attenuations to be set for the optical attenuating means 3 according to the optical power levels of higher- order diffracted lights at wavelengths obtained by a higher-order diffracted light power detecting means 5 so that the light intensities of lower-order diffracted lights at wavelengths may be equal. Corresponding lower-order diffracted lights outputted from the means 3 to the wavelengths are fed to an optical signal combining means 4 to output a wavelength-multiple signal 7 composed of optical signals at wavelengths λ1, λ2,..., λn.