The Amplified Spontaneous Emission (ASE) noise

equivalent spontaneous emission factor and equivalent noise factor for the Raman Amplifier (RA) as well as the respective impacts of the Signal Noise Ratio (SNR) for optical receivers on the ASE noise

Rayleigh noise

optical fiber length and switching gain in the RA are theoretically analyzed

and then the Double Rayleigh Backscattering (DRB) noise are also theoretically analyzed and calculated

furthermore

the numerically related simulations are also implemented. The calculation and simulation results show that: the RA

compared with the Erbium-Doped Fiber Amplifier (EDFA)

can improve the SNR of optical receivers under the condition of the same input signal; the equivalent spontaneous emission factor is less than 1 and will decrease with the increase of the switching gain

so this characteristics of the RA excels that of the EDFA; the condition that the Rayleigh noise of the RA can be ignored is that the gain of the RA is less than 15dB. In addition

some other significant conclusions to play an important role in guiding the optimal design of the RA are also obtained.