双向HFC网络设计关键技术.pdf

哈尔滨工程大学硕士学位论文摘要光纤同轴电缆混合网(HFC),采用了光纤与同轴电缆混合组成了传输网络的物理结构。光纤传输技术改变了传统的全电缆网络结构,采用HFC网结构的有线电视综合信息网不仅能带给有线电视更好的传输质量和更高的可靠性,更重要的是形成了一个性能良好的双向通信的基础结构。本文首先对HFC网的含义、基本网络结构、频谱安排、特点、局限性及应用等进行了介绍。在光纤同轴电缆混合网中,由于光纤的传输特性决定了传输系统的传输速率的提高,传输距离的加长和波分复用技术的实用化,因此又介绍了光纤的两大传输特性——损耗和色散特性。接下来也是本文的重点,讨论了有线电视双向HFC网络设计。影响双向 HFC系统传输质量的主要问题是来自于回传通道的噪声。在双向HFC系统中, 电缆传输部分一般是树枝状的拓扑结构,因此由用户终端和电缆设备引入的噪声在上行系统中产生严重的汇聚,造成所谓的“漏斗效应”,从而严重影响上行信道的性能。汇聚噪声包括各放大器产生的噪声成分(电缆双向放大器,光站输出放大器),各个用户终端产生和拾取的各种噪声成分。因此双向HFC网络的设计重点是如何减少回传链路各环节产生的噪声,避免“漏斗效应"给回传系统造成的影响。噪声汇聚、回传电平的均衡、回传电平的增益是影响回传接收质量的重要因素。最后通过大庆油田有线电视网改造工程实例的介绍实现了构建一个双向的有线电视综合信息网的目标。关键词:HFC;有线电视宽带信息网;有线电视双向HFC网络 ABSTRACT Hybrid Fiber--Coaxial(HFC)is work withthe physical structure ofthe fiberand coaxial optical transmisSion mcllIlology haschanged thetraditional structure oftheentire v∞ cabletelevision(CATV) using work callnot only hasthe11i吐transmission qualityandreliability,but alsocreate the importanttwo—munication infrastructurewith theprettyperformance. Inthispaper,the meaning ofthe work,and work structure,thespectrumarrangement,features,1imitations and applications work are described above a work,the transmission characteristics ofoptical fibertransmissionsystem determines theincreasing of thetransmission rateandtransmissiondistance,and thepractice ofwavelength division multiplexing(WDM)technology,SO thetwo main transmission characteristiesofthefiber-lOSS anddispersion arealsostatedhere. The focusofthispaper CATV work design. The noise from the return channel isthemain factor which affects the transmission quality ofthetwo-way HFC atwo-way HFC system,the cabletransmission section isthetypically tree-shaped topology noisefrom userterminals andthe cableequipment has asevere convergence inthe upgoing system,which resultsintheSO—called“funneIeffect'’.The“funllel effect', has apositive effect on upgoing converging noises consist ofthe ponent from different am