光无线宽带接入系统中的关键模块研究-物理电子学专业论文.docxVIP

I I 摘 要 光无线宽带接入是伴随着大功率半导体激光器和高灵敏度光电探测器件的日益完 善而重新兴起的一种无线接入方式，它综合了光纤通信和其它无线通信方式的特点，具 有高宽带、低成本、安装快捷、机动灵活等优点，因而在很多领域具有广阔的应用前景。 特别在解决光纤和局域网之间“最后一公里”接入问题上是一种经济合理的解决方案。 本文主要针对光无线宽带接入系统中的关键模块进行了研究，内容包括： (1) 广泛查阅国内外文献，对光无线宽带接入的特点及其应用作了全面阐述；简要介 绍了国内外在这方面的研究情况。 (2) 介绍光无线传输的大气信道的特点，着重分析了大气的散射、吸收和由大气湍流 引起的光强闪烁对光传输的影响，建立了光无线信道传输方程。 (3) 针对大气信道特点设计光无线宽带接入系统的接收模块。选择了光电探测器件， 设计了放大电路，分析了模块噪声，给出了模块优化的方案。 (4) 讨论了激光器的寿命与温度的关系，针对光无线宽带接入系统体积小、功耗低的 要求，设计了基于脉冲宽度调制（PWM）方式的激光器温度控制模块。比较了两种直 流稳压电源的特点，根据系统要求设计了电源模块。 (5)对光无线宽带接入系统的信道编码技术进行了分析，选择了编码方案，设计了编 解码模块，对系统在不同编码条件下的误码率差别进行了仿真，对仿真结果进行了讨论。 关键词： 光无线宽带接入 光强闪烁 前置放大电路 脉冲宽度调制 前向纠错 级联码 II II Abstract Optical wireless wide band access system, a kind of wireless communication, springs up once again along with the progress of the high power semiconductor lasers and optoelectronic detectors. Optical wireless access has many virtues such as large capacity, low cost, convenient deployment and flexibility since it integrates the advantages of fiber communication and other traditional wireless communication technologies. Optical wireless access has widely promising applications. Specially, optical wireless access system is a better method to solve the “last mile” problem between the LAN and fiber backbone. In this thesis, the main key modules of the optical wireless access system are focused on. The main contents of the thesis are: In the first chapter, the characters and applications of optical wireless access have been reviewed. The state of the art is also introduced in brief in this chapter. The characters of the atmospheric channel have been discussed, in which the atmospheric scatter, absorption and scintillation on the laser beam have been taken into account. And then the mathematical analysis model has been presented for optical wireless access in the atmospheric channel. The receiving module of optical wireless access system over the character of the atmospheric channel has been designed. The mechanism of selecting the propel detector and front am