Abstract: A multistage amplifier is disclosed for amplifying light over a wavelength band. A first and second span of amplifying fiber are optically coupled and a gain flattening filter (GFF) in-line with one of two spans of amplifying fiber is provided for attenuating certain wavelengths of amplified light. A first gain spectral response of the first and second spans of amplifying fiber including the GFF are measured over the wavelength band, and the shape of a ripple that oscillates as a function of wavelength in the form of a plurality of peaks or maxima and valleys in the form of minima occur at a plurality of different wavelengths, each different wavelength corresponding to a different channel. A second filter is provided finishing or compensating filter having a second spectral response that has a second plurality of peaks in the form of maxima and valleys in the form of minima is provided.

Abstract: A multistage amplifier is disclosed for amplifying light over a wavelength band. A first and second span of amplifying fiber are optically coupled and a gain flattening filter (GFF) in-line with one of two spans of amplifying fiber is provided for attenuating certain wavelengths of amplified light. A first gain spectral response of the first and second spans of amplifying fiber including the GFF are measured over the wavelength band, and the shape of a ripple that oscillates as a function of wavelength in the form of a plurality of peaks or maxima and valleys in the form of minima occur at a plurality of different wavelengths, each different wavelength corresponding to a different channel. A second filter is provided finishing or compensating filter having a second spectral response that has a second plurality of peaks in the form of maxima and valleys in the form of minima is provided.

Abstract: A method and system is disclosed of characterizing an optical amplifier for operation with a required tilt or curvature within predetermined limits. As the temperature of the erbium-doped optical amplifier is varied while a test signal is launched into the amplifier accompanied by a pump signal the output spectrum is compared with a desired spectrum. At different temperatures different measures of tilt or curvature are present at the output port of the amplifier in the presence of an input signal at the input port. Feedback related to the measure of tilt or curvature of at least one of the plurality of different temperatures is provided in the form of a feedback signal or an information signal.