Optimal design of flat-gain and flat-noise wide-band fiber Raman amplifiers

We theoretically analyze the influence of the forward pump lights on the flatness of gain and noise figure of bidirectional pumped fiber Raman amplifier and find a simple method to keep the flatness of gain and decrease noise figure at the same time through keeping the total integrals of forward and backward pump lights.And utilizing short wavelength lights as forward pump lights can suppress stimulated Raman scattering interaction between pump lights and get more reasonable power allocation of the pump lights.