Saturation and depletion effect of Raman scattering in optical fibers

The analytical solution of nonlinear power coupled equations involving three waves is given. The study reveals that the Raman gain saturation effect caused by the generation of the second Stokes has to be taken into consideration in light amplification by stimulated Raman scattering, though it can be ignored in spontaneous stimulated Raman scattering. It is also shown that it is advantageous to feed the fiber with a small low-order Stokes signal in amplifying the higher-order Stokes signal for easing the requirement of high pump power and long fiber length. A model to calculate higher-order Stokes radiation in low-loss optical fibers is presented