【作者】 李刚；

【导师】 王克家；

【作者基本信息】 哈尔滨工程大学 ， 光学工程， 2003， 硕士

【摘要】 光纤通信技术继续保持迅速的发展，从点到点的信息传输到网络应用，从干线网到用户网，正逐渐深入到通信的各个领域，各种新技术得到开发利用。码分多址技术在无线通信领域成功地得到大规模商品化应用，在光纤通信通信网中码分多址技术的应用近年来也吸引了许多研究者的兴趣，展现了很好的应用潜质。本文对码分多址技术在光纤通信系统中应用作了历史回顾与综合分析，总结出了若干关键技术问题，并作了深入的理论研究。 本文突破了以往在HFC系统中使用CDMA扩频技术通信时，通常都采用Gold序列来作为地址码的惯例，分析和提出了在HFC的特定环境中，使用同一m序列在某时刻具有的不同相移序列，来构成一个小区的地址编码，能够达到多用户通信时比使用Gold序列进行通信具有更好的相关特性。这种地址码的安排，要求用户间严格同步，使得原本为一个m序列的自相关函数，在各个用户相位差恒定的条件下，分割成用户间的自相关和互相关函数。论文在提出地址码设计方案后，通过计算机仿真实验，模拟一个用户数为100的小区，使用论文设计的地址码方案进行S-CDMA综合业务通信，已预先知道每个用户通信的信息，在计算机仿真通信处理完成后，检验在接收端的用户信息。通过验证每个用户在仿真处理后均能够恢复原始信息，证明了方案的正确性和可行性。 由于地址码的设计方案对用户间的地址码相位要求严格，本文对地址码相位同步问题也进行了深入的研究。论文所提出的方案是通过前端发射固定的导频信号，并且在前端和用户端都把用户地址码相位捆绑在导频相位上，使得用户在同步捕获和跟踪导频相位后，间接得到用户的地址码相位。我们成功设计了导频参考时间点0的电路图，从而解决了S-CDMA系统对同步的严格要求。同时，我们还提出了用两次停留搜索方法代替一次串行搜索进行同步的方法，使导频的同步搜索效率得以提高，并通过计算机仿真实验进行了验证。 本文还对光码分多址通信系统中的光纤非线性效应进行了深入研究。论哈尔滨工程大学硕士学位论文文推导综合了各种非线性效应的非线性薛定愕方程;并提出了当各种非线性效应都作为微扰时，它们的影响可以简单地将各自的作用加到方程之中，这样就可以得到总结性的方程。然后本文又继续讨论各种非线性效应在不同实际情况中影响的大小及对方程的简化。根据综合研究非线性效应的考虑，本文研究了自相位调制及交叉相位调制对四波混频相位匹配的影响，在一定的简化下得到了解析的结果。结果表明相位调制对四波混频的效率会有影响，用四波混频进行波长转换时该情况有很大作用。如果忽略相位调制的影响(光功率很小时)，那么效率公式就回复到通常的仅由色散及频道间隔决定的情况。更多还原

【Abstract】 Optical fiber communication keeps in rapid development, from trunk lines to subscriber networks , stepping into more and more areas of the modern communication . While code-division multiple-access technology has been employed commercially world wide , its application in fiber-optic network become attractive . In this dissertation , the researches on the application of CDMA in fiber-optic communication systems have been reviewed , and several key techniques in the application are proposed with theoretical analysis.In traditional researches and applications of the HFC CDMA communication system , the GOLD sequence was used as the users’ address code . In this paper , we analyze the characteristics of the m sequence in detail . Then , the address code can be designed by different phase sequence of an m sequence . Our studied method can attain better communication quality than before case . Of course , synchronization among all users is requested , i.e., our method is a S-CDMA communication . The self-correlation function of the m sequence is divided into the self-correlation between all same address users and the mutual-correlation between all different address users . A computer simulation experiment , which 100 users are communicating under our method , is given in this paper . The information of every user is known before the processing of S-CDMA communication start . After S-CDMA processing , the demodulated information and the original information of the same users are equally . We found that they are same in every user and prove the right of our method .In our communication method , synchronization between all users is requested . The key is that the Head-end emits the guide m sequence , which is non-correlative with any users’ address code . The phase of all users address code and the Head-end address code are combined with the guide m sequence . Everyuser address code phase can attain after the guide m sequence phase is searched and tracked . After the circuit that can offer the point "0" of time coordinate is designed by myself, the most difficulty of our S-CDMA communication system is solved . In search processing of synchronization , one time search processing is improved by two time search processing . Therefore , the time spend on synchronization is saved , not only in the theory analysis but also in the computer simulation experiment are shown in this paper .The nonlinear effect has also been researched deeply in this paper . The nonlinear Schrodinger Equation (NLS) that consider all kinds of the nonlinear effects is derived . When every nonlinear effect is processed as perturbation , they can be simply put in the equation altogether . Then the different influence of each effect is discussed under different condition . By following the way of studying the nonlinear effect as a whole , the influence of the SPM and XPM to the phase matching condition of FWM is studied . From the achieved analytical expression it can be seen that the phase modulation can change the efficiency of the FWM . It is very important to the wavelength conversion through FWM . The result shows that a shorter fiber is necessary to get an enough efficiency when employing high optical energy.更多还原