【作者】 汪洋；

【导师】 于晋龙；

【作者基本信息】 天津大学 ， 通信与信息系统， 2007， 硕士

【摘要】 随着光纤传输速率的提高,由偏振模色散(PMD)导致的脉冲展宽的问题将越来越严重。为了补偿传输线路中的PMD效应,本实验室已做了几年的理论研究。在前人理论研究的基础上,本课题采用了前向反馈的动态补偿方案,在实验室实现了PMD的动态补偿。其中本人主要负责电路控制补偿部分的研究、设计及实现,具体工作如下:1.提出以FPGA为控制核心的硬件电路设计方案,并进行芯片选型、电路原理图设计,六层PCB布局和布线,芯片和元器件的焊接。为整个电路控制系统提供了一个硬件平台;2.在FPGA中,通过Verilog语言,采用流水线设计技术,快速实现了PMD理论中相关物理量的计算;同时构建了Nios II嵌入式软核,提出了有效的动态补偿算法,并通过C语言实现;3.提出了三维坐标系旋转变换理论并进行相关公式的推导,实现了对偏振控制器的有效控制;4.进行了两个关键性实验的研究:偏振稳定实验和PMD动态补偿实验。偏振稳定实验的成功为PMD动态补偿实验提供了强有力的保障,其偏振稳定精度最高达可到0.5度,偏振稳定响应时间最快可达5ms。本系统的优点是:实现了PMD的动态补偿,补偿速率较快。并且提出的动态补偿方案是光速率透明的,即无论光的速率是多少都能通过本方案进行PMD的动态补偿。本系统的不足是:对于判别传输线路中快慢轴的问题,从理论上我们还没有找到合适的方法。针对本系统的不足,我们提出了一种将前向反馈系统和后向反馈系统相结合的改进方案,即在本系统方案的基础上增加了一套后向反馈机制,以解决传输线路快慢轴的判别问题。更多还原

【Abstract】 As the increase of the optical transmission speed, the problem of pulse broadening caused by Polarization Mode Dispersion (PMD) will be more and more serious. In order to compensate the PMD influence, several years theory research had been taken in our laboratory. On the bases of the research, the forward feedback dynamic compensation scheme was adopted in our project, implementing the dynamic PMD compensation. My job is mainly concerned with the research, the design and the implement of circuit for compensation control. Specifically speaking:1. The proposal of the hardware design with FPGA as the control centre, the selection of IC, the circuit schematic design, the layout and fitting on PCB, the jointing of IC and components. All of these provided a hardware build-up for the whole circuit control.2. In FPGA, some PMD theory values were fast computed by Verilog HDL programing with the pipelining technology. The Nios II Embedded soft CPU was constructed in FPGA and efficient dynamic compensation algorithm was put forward by C language.3. Three dimension coordinate system turning transforming theory was proposed and the related formula was deduced, which promoted the effective control for Polarization controller (PC)The advantages of our project: PMD dynamic compensation was implemented with high speed. The project was independent of transmission speed. That is, the project can work successfully at whatever transmission speed.The disadvantage of our project: We haven’t found an effective way from theory for the judgement between fast-axis and slow-axis of transmission line.Concerning the disadvantage, we put forward another scheme which was the integration of the forward feedback system and backward feedback system. That is, a backward feedback mechanism was considered on the basis of our current project.更多还原