【作者】 孔庆花；

【导师】 王胜坤；

【作者基本信息】 太原理工大学 ， 电路与系统， 2003， 硕士

【摘要】 本论文主要讨论了光纤非线性效应当中的一种——受激喇曼散射，以及基于受激喇曼散射的应用——喇曼放大器的噪声特性。在前人讨论的基础上，本论文着重在以下的工作上有所进展： 综述了喇曼放大器的构成、对各部件的要求、工作原理，喇曼放大器的特性以及喇曼放大器的应用。在此基础上，分析了喇曼放大器前向泵浦和后向泵浦的区别；得出最佳泵浦值点；进而进一步阐述喇曼放大器的局限性。 受激喇曼散射是光纤本身的一种光学非线性效应。根据受激喇曼散射的原理，利用麦克斯韦方程组，推导出了在喇曼放大器中信号光和泵浦光的耦合方程——包括光强耦合方程和光功率耦合方程。在此模型的基础上，进而分析喇曼放大器的各项参数对系统误码率的影响。在误码率的基础上，得出分析系统功率代价的数学模型。据此数学模型，得出这样的结论：系统的入射功率、系统中的复用信道数的增加都会使信道间的非线性作用加强，导致系统的功率代价上升；喇曼放大器的级数的增多也会使系统功率代价增加。 我们分析的各种数学模型都是基于小信号的情况。在实际的工程应用当中，趋向于大信号的情况。本文通过信号传输的数学模型，分别分析了在大小信号时系统的输出信号情况以及非线性对大、小信号的不同影响。 最后，讨论了多信道情况下系统中的串话系数。串话系数也是衡量信道间非线性作用大小的参数。分析了各种参数对串话系数的影响。据此串话系数，分析得出了模拟系统和数字系统个参数的极限值。 在喇曼放大器中，存在很多噪声。在本论文中，讨论了两种噪声：自发辐射噪声和瑞利散射噪声。大原理工大学硕士研究生毕业论文 自发辐射噪声是放大器噪声中一种比较重要的噪声。通过对数学模型的讨论，可知ASE跟放大器的增益有线性关系。 噪声指数是衡量放大器对光通信系统影响的一个重要参数。在小信号单泵浦光情况下，通过对比有瑞利散射和无瑞利散射时放大器的噪声指数，可知在无瑞利散射的情况下，放大器的噪声指数随放大器增益是逐渐下降的。也就是说，放大器的使用使系统的光信噪比提高，系统性能优化。而瑞利散射使噪声指数随放大器增益增大，使放大器性能变坏。而且，得出了一个最佳泵浦点。即瑞利散射开始对放大器起破坏作用的点。此值在工程应用中具有及其重要的意义。另外，还分析了双向泵浦和多泵浦时的噪声指数，及各参数对噪声指数的影响。在实际的工程应用中，使用EDFA+FRA的模型，通过对比此模型和EDFA，得出了这两种模型在光信噪比方面的改进。可见，使用EDFA+FRA的模型比EDFA模型能改进系统的性能。更多还原

【Abstract】 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.更多还原