A flattened gain amplifier has a waveguide with a core doped with at least one species of rare earth ion. The rare earth ion has a gain profile with a first gain in a first wavelength band and a second gain in a second wavelength band. The flattened gain amplifier also has a first grating and a reflective element optically coupled to the core. The positions of the first grating and reflective element along the length define a first amplifying length and a second amplifying length. The ratio of the first amplifying length to the second amplifying length is about equal to the ratio of the second gain to the first gain.