【作者】 王凯；

【导师】 李蔚；

【作者基本信息】 华中科技大学 ， 物理电子学， 2009， 硕士

【摘要】 本论文提出了一种新颖的全光正交频分复用（OFDM,Orthogonal Frequency Division Multiplexing）系统,研究了该系统中基于光耦合器的光离散傅里叶变换（DFT,Discrete Fourier Transform）器件。OFDM对于无线和铜线的应用,已经是成熟的技术,而在光通信上的应用,却还是比较晚的事。但OFDM的光传输是一个快速发展的研究领域。在非全光OFDM系统中,容量受限于两个主要方面:光数据调制器、光电二极管,和快速傅里叶变换（FFT,Fast Fourier Transform）的电路。而在全光OFDM系统中,FFT以光的方式实现,传输数据率就会大大提高。全光OFDM技术有着很大吸引力,作为以后的大容量、高频谱效率、长距离通信系统的有力候选技术。本论文首先对OFDM原理在数学上进行了分析,并根据无线应用中OFDM系统的基本功能,讨论了OFDM的关键技术。然后针对全光OFDM系统,本论文采用了一种基于光耦合器的DFT器件。根据光耦合器的输入输出关系,给它加上适当相移,可以实现两个点的DFT,并作为光DFT基本单元。然后按照FFT算法的思想,用基本单元构造出了N （2的整数次幂）个点的DFT器件。并给出了具体的实现结构和基于平面光路（PLC,Planar Lightwave Circuit）的仿真。接着提出了基于上述器件的全光OFDM系统,对系统的各个部分及其工作过程做出了细致的说明。对这种全光OFDM系统在160Gbit/s速率下进行了仿真,结果表明接收端的误码率为7.958×10^-10,接收机前的光信噪比为24.97dB。并进行了性能仿真,主要是分析了不同调制方式下色散和噪声的特性,以及非线性对全光OFDM的影响。更多还原

【Abstract】 This thesis proposes a novel all-optical Orthogonal Frequency Division Multiplexing （OFDM） transmission system, and studies optical Discrete Fourier Transform （DFT） devices based on optical couplers in this system.OFDM has been established as a mature technology for applications of wireless and copper, while it is lately applied to optical communication. But optical transmission by OFDM is the fastest growing area in recent years. In not-all-optical OFDM system, the capacity is limited by two major components: the optical data modulator and the photodiode, and electronics for FFT. While in all-optical one, the FFT process is achieved in optical domain, the OFDM transmission data rate can be increased by far. All-optical OFDM becomes an attractive candidate for high capacity, frequency effective, long haul communication systems.This thesis firstly analyses the mathematical principle of OFDM, and discusses key technologies related to basic functions of wireless OFDM system.Then, this thesis applies a kind of optical DFT devices based on optical couplers in accordance with all-optical OFDM system. And shows that one coupler can act as a 2×2 DFT device when combined with appropriate phase shift, owing to the relationship between its inputs and outputs. Taking it as the basic unit, a N×N DFT device is constructed according to FFT algorithm. We also show the detailed structure and simulation of DFT devices based on Planar Lightwave Circuit （PLC）.Next, this thesis proposes a novel all-optical OFDM system based on the devices mentioned above. The function of each section and operation processes of system are illustrated. A simulation of this all-optical OFDM system at 160Gbit/s is conducted. The results give BER of 7.958×10^-10 and OSNR of 24.97dB both at receiver. Also performance simulations are implemented, which consist of dispersion character and noise characteristics of different modulation and nonlinear effect in all-optical OFDM system. The feasibility of the system is demonstrated.更多还原