Coupled-mode theory of Raman amplification in lossless optical fibers

Abstract

Raman amplification in weakly guiding optical fibers is investigated for the two cases of weak and strong mode coupling. Use is made of the statistical ensemble of similar fibers introduced by Marcuse for studying mode coupling in optical waveguides. In the weak-coupling case, the Stokes powers of different modes increase independently, and the gain of each mode depends on the initial poewrs of all laser modes. In the strong-coupling case, power equipartition between Stokes modes takes place throughout the fibers, and the common gain is the average of the individual mode gains.