ABSTRACT
The Raman effect is an inelastic scattering of light with optical phonons of matter, through which light emerging from a matter downshifts in the frequency from the incident light. Fiber Raman amplifiers are a kind of optical amplifier that exploits stimulated Raman scattering in fiber for amplifying optical signals propagating through optical fiber. A chief virtue of fiber Raman amplifiers is that gain is supplied in transmission fiber itself. The main design issues of fiber Raman amplifiers are gain, gain ripple, optical signal-tonoise ratio, noise figure, the amount of double Rayleigh backscattering, nonlinear phase shift, and pump mediated noise. In optical fiber, there is always some portion of propagating signal reflected back due to the Rayleigh scattering. Because of the relatively long length of gain fiber, Raman amplifiers are likely to suffer from double Rayleigh backscattering, in which the signal undergoes twice the Rayleigh backscattering.
