rectly by considering only quantum noise, but it is needed to take into account other phe- nomena that can be as important as quantum noise. The first is related to the fact that Raman scattering is practically an instantaneous phe- nomenon on the typical time scale of telecommunication systems. This means that gain saturation due to signal is effective in reducing signal dynamics since gain is high when the input power is lower, that is, when a "zero" is transmitted, while when signal is high (i.e., a "one" is transmitted), the gain is smaller due to saturation. This phenomenon, however, is very fast and no other signal distortion is implied. If the signal dynamic decrease can be managed by using high power suppression correspondence of zeros, more dangerous is the fact that any amplitude fluctuation of the pump, also the intensity noise that is present in all the semiconductor lasers, reflects in a fluctuation of the Raman gain. This creates the second important noise source that is called pump relative intensity noise (RIN) transfer [68]. Telecommunication Networks A third noise source is the so-called double Rayleigh scattering constituted by multiple ASE reflections that create an incoherent ASE contribution to the overall noise. Naturally, the component due to two reflections, one backward and the other forward, is the greater and usually the only one that is needed to have a good description of the noise in the amplifier. Finally, a fourth source of noise arises from the so-called phonon-stimulated optical noise. This effect is due to the population of thermally induced phonons in the glass fiber that spontaneously experience gain from the pumps, thereby creating additional noise for signals close to the pump wavelengths. It has been shown that this effect can lead to an increase in noise figure of up to 3 dB for signals near the pump wavelength [69]. In order to analyze the impact of different pumping schemes and to correctly foresee the amplifier noise properties, a model of a concentrated Raman amplifie