The Study Of The Noise Feature Of Fiber Raman Amplifier Based On Stimulated Raman Scattering

This paper mainly discusses one of the fiber' s nonlinear effects-Stimulated Raman Scattering(SRS), and the noise feature of Fiber Raman Amplifier (FRA) based on the SRS. On the basis of existing research, this paper has innovation as follows:It summarizes the structure of FRA, the request to the parts of FRA, its work principle, its feature and the application of FRA. On the basis of this , this paper analyzes the differences between forward-pump and backward-pump, gets the best pump-point ?and discusses the limitation of FRA.SRS is a kind of nonlinear effect of fiber itself. Coupled equation of pump wave and signal wave basing on MAXWELL equation is got, including light intention coupled equation and light power coupled equation. On the basis of this model , the effect that the parameters of FRA have on the rate of error code is analyzed. Based on the rate of error code, the model of power cost is got. According to this model, the conclusion that the increase of the incidence power of fiber communication system and the number of channels can enhance the nonlinear effect between channels and can increase power cost of the system is got. On the other hand, the number of FRA can increase power cost of system, too.Under the common condition, all kinds of models are discussed based on small signals. In actual situation, signals are often very big. This paper also discusses big signals' nonlinear effect to thesystem.Besides, this paper discusses crosstalk coefficient in multi-channel system and analyzes the effect that some parameters have on the crosstalk coefficient. According to this, the limited value of digital and analog system are gained.There are a lot of noise in FRA. In this paper, two kind of noise are discussed:Amplifier Spontaneous Eradiation(ASE) and Rayleigh Back Scattering(RBS).ASE is a more important noise in FRA. According to the discussion, the conclusion is got that relation between ASE and Gain of FRA is linear.Noise Figure (NF) is an important parameter that weigh the FRA' s effect to the fiber communication system. Under the condition of small signal and single pump, the conclusion is got that the NF of FRA decreases with the increase of Gain of FRA under the condition of non-RBS. That is to say, the use of FRA make SNR of system increase. But the RBS make NF increasing with the Gain of FRA and make the performance of FRA bad. According to this, the best pump point is got. The point is very important in the actual application. Besides, this paper analyzes NF when the pumps are bi-direction and analyzes parameter' s effect to NF. In actual application, the model of FRA+EDFA is more widely used than EDFA. This paper expounds the improvement of FRA+EDFA.