【作者】 张军；

【导师】 陈林；

【作者基本信息】 湖南大学 ， 计算机应用技术， 2013， 硕士

【摘要】 随着通信技术的快速发展，人们对通信质量的要求也越来越高。如何在有限的带宽下实现信息的高速率、大容量、优质量传输引起了研究者们的极大关注。光正交频分复用(OFDM)技术作为一种频谱利用率高、对光纤色散及偏振模色散容忍度强的调制技术而成为研究的热点。而光OFDM技术与无源光网络技术(PON)相结合成的OFDM-PON结构拥有灵活的动态带宽分配方式，对传输业务透明以及与现有网络的兼容好等优点是下一代或者未来接入网中的关键技术之一。从无线领域中的OFDM技术基本原理入手，简要的介绍了OFDM关键技术以及优点与不足之处。并对一种典型的强度调制直接检测光OFDM(IM/DD-OOFDM)传输系统的工作原理进行了较为详细的说明。分别对激光器相位噪声及马赫-曾德尔调制器(MZM)直流偏置对传输性能的影响做了较为深入的理论分析，并在此基础上展开了以下三部分研究工作以及所得到的研究成果：(1)使用Matlab对OFDM调制与解调、激光器相位噪声模型、MZM传输模型、光纤色度色散信道模型等实现了数学建模，为研究分析IM/DD-OOFDM传输系统中激光器相位噪声及MZM直流偏置的影响提供可行的仿真平台。(2)研究了IM/DD-OOFDM系统中激光器相位噪声受光纤色度色散作用后转换为强度噪声，其中高频子载波受到的干扰较大，子载波间的正交性受到不同程度的破坏。并针对这种损伤机制提出使用自适应功率/比特分配方法或者预增强技术以减轻激光器相位噪声的影响。(3)分别从理论、数值仿真及实验的角度研究并分析了MZM工作在不同调制指数下不同直流偏置对光OFDM接收机的灵敏度的影响，依据不同调制指数通过优化MZM直流偏置可以在很大程度上提高接收机的灵敏度。更多还原

【Abstract】 With the rapid development of communication technology, people become moreurgent to demand for communication quality. How to realize information transmissionwith high speed, large capacity and high quality at limited bandwidth draws greatattention of researchers. As an important modulation technique, optical orthogonalfrequency division multiplexing (OOFDM) with high spectral efficiency, and hightolerance of fiber optic dispersion and polarization mode dispersion (PMD) hasbecome a research hotspot. And the passive optical network (PON) based OFDMtechqnie combined the OOFDM technique with passive optical network (PON) withthe advantage of flexible dynamic bandwidth allocation, variable services transparenttransmission and compatible with the existing network, thus it is one of the keytechniques for optical access network in the next generation or near future.Under the knowledge of basic principle of OFDM technology in the wirelesscommunications, the key techniques, the advantages and disadvantages of OFDM arebriefly introduced. And a detailed description for the operation principle of a typicalintensity modulation with direct-detection optical OFDM (IM/DD-OOFDM)transmission system.An in-depth theoretical analysis of the effect of laser phase noise and the bias ofMach-Zehnder modulator (MZM) on the transmission performance. On this basis, thefollowing three parts of research work and related achievements are show below:(1) Implentment of the mathematical modeling of OFDM modulator anddemodulator, MZM, chromatic dispersion of fiber optic etc. in order to provide afeasible simulation platform to analyze the effects of laser phase noise and bias ofMZM in IM/DD-OOFDM transmission system.(2) The Laser phase noise with chromatic dispersion of fiber in IM/DD-OOFDMsystem is converted to intensity noise, and the higher frequency subcarrier, theinterference is larger, the orthogonality between subcarriers are subject to differentdegrees of damage. According to the mechanism of damaged effects, using adaptivepower and bit allocation or the pre-emphasis technique is proposed to reduce the effectof laser phase noise.(3) The study and analysis of the effects on the OFDM receiver sensitivity withMZM at different modulation index under various dc bias by employing the theories,numerical simulation and experiments respectively, then according to different modulation index to optimize bias of MZM to improve the sensitivity of receiver tosome extent.更多还原