Patent ID: 8045258

Claim:
A method for selecting a relation between a gain G f of a Forward Raman Amplifier (FRA) at a transmitting end of a fiber optic transmission line and an optical signal to noise ratio (OSNR) at a receiving end of the fiber optic transmission line, provided that said transmission line operates under a non-linearity limit, and power loss L of the fiber optic transmission line is much greater than a selected value of the gain G f ; the method comprises selecting said relation by using a regulation function R OSNR of OSNR improvement, defined substantially close to the following expression: R OSNR =G f /R NL (1) where R NL is a factor of the FRA, calculated substantially close to the following: R NL =μG f (ln( G f )) −μ [Γ(μ)−Γ(μ,ln( G f ))] (2) where μ=α/β, α is the fiber attenuation at the signal wavelength, β is the fiber attenuation of the Raman pump wavelengths, Γ(x) and Γ(x, y) are the Gamma and the incomplete Gamma functions, respectively.