The increasing demand of wide band internet services has led the research to improve optical networks also outside the conventional C-band. In this frame, Raman amplifiers play a critical role being able to provide amplification at any wavelength. This paper investigates the properties of Photonic Crystal Fiber based Raman Amplifiers. An accurate Raman amplifier model, suitable for any kind of germano-silicate photonic crystal fibers, has been implemented. Starting from the photonic crystal fiber design, by using a full vectorial solver based on the finite element method, it is possible to calculate the Raman gain coefficient and the Rayleigh backscattering coefficient of the fiber. Therefore, by solving the coupled equation system that describes the Raman amplification in optical fibers, it is possible to evaluate the gain spectrum at the end of the fibre. The mathematical model includes stimulated Raman scattering and its amplification, the spontaneous Raman emission and its temperature dependance, the Rayleigh backscattering, the fiber loss, and the arbitrary interaction within pumps signal and noise from either propagation directions. The fundamental role of background losses is highlighted. The study is focused on multi-pump configuration to obtain a flat gain spectrum. Considering a practical photonic crystal fiber, with d/Λ = 0.625 and Λ = 4 μm and varying the number of pumps, their wavelength and power, the shape of the gain spectrum has been adjusted to provide a flatness of 0.5 dB from 1540 nm to 1572 nm.