【作者】 王鼎；

【导师】 刘德明；

【作者基本信息】 华中科技大学 ， 光电信息工程， 2007， 硕士

【摘要】 近几年来,随着高清电视,视频会议,数字影院和高质量音频传输服务的出现,接入网需要向高容量、高质量的方向发展。然而现存的下层接入网却存在带宽较小,网管损耗较大等问题。作为接入网的一个重要组成部分,有线电视(CATV)传输网络也不例外。目前,中国广电总局正在大力改造原有的混合光纤同轴形式的接入网,向光接入网发展,拓展光纤传输链路。而如何补偿信号在分级传输中的损耗是其中的一个重要问题。目前广泛商用的掺饵光纤放大器工作在1550nm窗口,这与现存的工作在1310nm窗口的CATV光发射机不兼容。因此就需要另一种放大器来实现接入网中的光放大。半导体光放大器(SOA)可以工作在1310nm窗口。半导体材料和器件的发展促使增益钳制(GC) SOA技术逐渐成熟。而线性放大器(LOA)概念的提出又标志着SOA在线路放大的应用中取得了新的进展。目前对于LOA的研究主要集中在波分复用信号的放大上,对CATV这种射频副载波信号的放大还没有相关的研究。本文介绍了带有SOA放大的CATV传输系统,并分析了SOA引入的非线性失真特性和噪声特性。本文首次建立了计算SOA中载流子浓度调制效应引起非线性失真的基本模型,计算了SOA引入的综合二阶失真(CSO)的大小,并通过实验验证,得出非线性失真大小和SOA工作条件的基本关系。本文还实验分析了SOA引入的噪声和SOA的工作条件以及系统CNR的关系。GC-SOA或LOA将在今后的接入网和微波光网络的发展中发挥重要左右。本文最后分析了GC-SOA减小非线性失真的基本原理,为进一步研究GC-SOA或LOA的非线性失真打下了理论基础。更多还原

【Abstract】 Emerging applications in recent years, such as high-definition TV, tele-presence, digital cinema and high-quality audio transmission demand high-throughput optical access networks (OAN) with Quality of Service requirements. Nevertheless, the infrastructure of current access networks suffers from limited bandwidth and high network management cost. Cable television (CATV), one of the major services in OAN, is no exception. An evolution in access network is now proposed by the Chinese administration of radio film and television, changing the hybrid fiber coaxial networks to optical access networks. However, the requirement of optical amplifier to expand fiber links is confronted with a dilemma– commercial fiber amplifiers only operate in the wavelength region near 1550nm while the existent lasers operate near 1310nm.Semiconductor optical amplifier (SOA) can operate in the wavelength region near 1310nm. Progresses in semiconductor materials and devices accelerated the maturity of gain-clamped (GC) SOA. And with the concept of linear optical amplifier (LOA) being brought out, SOAs are now prepared for inline amplification. Recent works on LOA are mainly focused on the amplification of WDM signals; so far, no work is carried out on the amplification of RF subcarrier multiplexed signal, as CATV signals.In this dissertation, CATV lightwave systems with SOA for amplification is presented, and the SOA induced nonlinear distortion and noise are studied. A calculative model of nonlinearity based on carrier-density modulation in SOA is for the first time presented and used to calculation the composite second-order (CSO) index. The numerical results, as well as experiments, show a strong dependence of SOA induced CSO on input power and injected current– higher input power and lower injected current are required for better CSO. The SOA induced noise is also investigated; experiments confirm the theory analysis– output carrier to noise ratio is proportional with the noise figure of SOA, which can be optimized by the increases of the input power and injected current.Gain-clamped semiconductor optical amplifiers or linear optical amplifiers are promising components in future OAN and microwave photonics links. Further study shows and explains the reduction of nonlinear distortion utilizing gain-clamped SOAs instead of conventional SOAs. Theoretical analysis in this dissertation paves the road for further research on the nonlinear distortion of GCSOA or LOA.更多还原