Optical fiber amplifier with periodic gain and refractive-index corrugations

An optical fiber amplifier is proposed in which both the gain and refractive index are corrugated in the shape of a periodic square function along a longitudinal direction. Amplifying characteristics are numerically investigated for both continuous and pulsed waves as a typical example of a multimode optical fiber. As a result, choosing both corrugation periods close to the Bragg reflection condition and the fiber length leads to a unique amplifier that has various features such as high gain, frequency selectivity, and rejection of mode dispersion.