Patent ID: 7006280
Filing Date: 2006-02-28
Classification: H01S

Abstract:
1. A multistage amplifier for amplifying light over a wavelength band comprising: a first span of amplifying fiber; a second span of amplifying fiber optically coupled with the first span; a gain flattening filter (GFF) for attenuating certain bands of the output spectrum more than others, to attempt to provide a flatter output response in-line with at least one of the first and second spans of amplifying fiber for attenuating predetermined wavelengths of amplified light, WHEREIN A FIRST gain spectral response of the first and second spans of amplifying fibre including the GFF measured over the wavelength band has shape of a ripple that oscillates as a function of wavelength such that a plurality of peaks in the form of maxima and valleys in the form of minima occur at a plurality of different wavelengths, each different wavelength corresponding to a different channel; and, a second gain flattening compensating filter for attenuating certain bands of the output spectrum more than others, to attempt to provide a flatter output response in-line with one of the first and second spans of fiber having a SECOND spectral response that has a second plurality of peaks in the form of maxima and valleys in the form of minima, wherein the second spectral response is absent at least 50% of four most predominant peaks or valleys at channels where peaks or valleys, respectively, were present in the first spectral response, and WHEREIN a maximum ripple amplitude in the second spectral response is less than a maximum ripple amplitude in the first gain spectral response.