毕业论文外文翻译--光纤通信系统仿真及常用通信接口技术.doc

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1、摘要本文介绍了光纤通信的发展方向，阐述了系统仿真的特点及国内外的发展状况，第二部分为现用通信接口中常用接口讨论。关键词： 光纤通信，发展方向，系统仿真，接口1 概述1.1 光纤通信在“信息高速公路”的概念被提出以后，光纤通信技术在加大容量和延长通信距离方面取得了突飞猛进的发展。宽带光纤放大器W-EDFA（Wide band Erbium-Doped Fiber Amplifier）和密集波分复用是光纤通信技术发展最引人瞩目的方向。为了降低损耗和色散设计了色散位移光纤DSF（Dispersion Shifted Fiber），在1525-1565nm波段内，色散降至2-3ps/（nmkm）间；在

2、1540nm色散为零。为减小DWDM系统的四波混频效应，还设计了一种新型的非零色散光纤NZDF（Non-Zero Dispersion Fiber）。与此同时，光电子集成技术（OEIC）也在飞速发展，垂直腔面发射激光器VCSEL（Vertical Ca-vity Surface Emitting Laser）和光电接收机已经实现了光电子集成。光的时分多种（OTDM）目前国际上也有单位积极从事研究。光纤常被电话公司用于传递电话、互联网，或是有线电视的信号，有时候利用一条光纤就可以同时传递上述的所有信号。与传统的铜线相比，光纤的信号衰减与遭受干扰的情形都改善很多，特别是长距离以及大量传输的使用场合

3、中，光纤的优势更为明显。然而，在城市之间利用光纤的通信基础建设通常施工难度以及材料成本难以控制，完工后的系统维运复杂度与成本也居高不下。因此，早期光纤通信系统多半应用在长途的通信需求中，这样才能让光纤的优势彻底发挥，并且抑制住不断增加的成本。从2000年光通信市场崩溃后，光纤通信的成本也不断下探，目前已经和铜缆为骨干的通信系统不相上下。对于光纤通信产业而言，1990年光放大器正式进入商业市场的应用后，很多超长距离的光纤通信才得以真正实现，例如越洋的海底电缆。到了2002年时，越洋海底电缆的总长已经超过25万公里，每秒能携带的数据量超过2.56Tb，而且根据电信业者的统计，这些数据从2004年后

4、仍然不断的大幅成长中。1.2光纤通信的历史1966年查尔斯KKao和乔治hockom在位于英国哈洛区的STC实验室(STL)提出了光纤，他们表示，在现有玻璃中拥有 1000 dB/km损失 (对比于同轴电缆的5-10 db/km)应归结于污染物，可能会被潜在地去除。1970年代康宁公司成功的开发出高品质低衰减的光纤，此时信号在光纤中传递的衰减量第一次低于光纤通信之父高锟所提出的每公里衰减20分贝关卡，证明了光纤作为通信介质的可能性。与此同时使用砷化镓作为材料的用于长距离传送的半导体激光也被发明出来，并且凭借着体积小的优势而大量运用于光纤通信系统中。从1975年开始的一段研究时期过后，第一个光纤

5、通信系统诞生了，使用波长800纳米并且使用砷化镓激光作为光源。这个第一代系统传输的速率达到45Mb/s，每10公里需要一个中继器增强信号。很快于1977年4月22日，在加利福尼亚的长滩普通电话和电子通过光纤通信以6 Mbit/s传输速率送出了第一通现场连接的通话业务。第二代的商用光纤通信系统也在1980年代初期就发展出来，使用波长1300纳米的磷砷化镓铟激光。早期的光纤通信系统虽然受到色散）的问题而影响了信号品质，但是1981年单模光纤的发明克服了这个问题。到了1987年时，一个商用光纤通信系统的传输速率已经高达1.7Gb/s，比第一个光纤通信系统的速率快了将近四十倍之谱。同时传输的功率与信号

6、衰减的问题也有显著改善，间隔50公里才需要一个中继器增强信号。1980年代末，EDFA的诞生，堪称光通信历史上的一个里程碑似的事件，它使光纤通信可直接进行光中继，使长距离高速传输成为可能，并促使了DWDM的诞生。第三代的光纤通信系统改用波长1550纳米的激光做光源，而且信号的衰减已经低至每公里0.2分贝。之前使用磷砷化镓铟激光的光纤通信系统常常遭遇到脉波延散问题，而科学家则设计出色散迁移光纤来解决这些问题，这种光纤在传递1550纳米的光波时，色散几乎为零，因其可将激光光的光谱限制在单一纵模。这些技术上的突破使得第三代光纤通信系统的传输速率达到2.5Gb/s，而且中继器的间隔可达到100公里远。

7、第四代光纤通信系统引进了光放大器，进一步减少中继器的需求。另外，波分复用技术则大幅增加传输速率。这两项技术的发展让光纤通信系统的容量以每六个月增加一倍的方式大幅跃进，到了2001年时已经到达10Tb/s的惊人速率，足足是80年代光纤通信系统的200倍之多。近年来，传输速率已经进一步增加到14Tb/s，每隔160公里才需要一个中继器。第五代光纤通信系统发展的重心在于扩展波分复用器的波长操作范围。传统的波长范围，也就是一般俗称的“C band”约是1530纳米至1570纳米之间，新一带的无水光纤低损耗的波段则延伸到1300纳米至1650纳米间。另外一个发展中的技术是引进光孤子的概念，利用光纤的非线

8、性效应，让脉波能够抵抗色散而维持原本的波形。1990年至2000年间，光纤通信产业受到互联网泡沫的影响而大幅成长。此外一些新兴的网络应用，如随选视频使得互联网带宽的成长甚至超过摩尔定律所预期集成电路芯片中晶体管增加的速率。而自互联网泡沫破灭至2006年为止，光纤通信产业通过企业整并壮大规模，以及委外生产的方式降低成本来延续生命。现在的发展前沿就是全光网络了，使光通信完全的代替电信号通讯系统，当然，这还有很长的路要走。1.3 系统的仿真 系统仿真是近二十年发展起来的一门新兴技术科学。所谓计算机仿真就是在计算机上利用模型对实际系统进行实验研究的过程。利用计算机仿真可以多次重复模拟客观世界的同一现象

9、，从而得以找出其内在规律。尤其对含有随机变量和随机过程，难以建立数学模型的客观事物的研究，计算机仿真方法具有突出的优点，已成为分析、研究和设计各种系统的重要手段。把计算机仿真技术应用到通信领域就是其中的一项重要分支。随着通信技术的发展，通信网络的数量和复杂度的迅速增长，在通信系统设计中运用计算机仿真技术已成为新系统设计时缩短设计周期、提高设计可靠性和已有系统性能改进的不可缺少的工具。2 光纤通信系统的仿真 光纤通信技术是一门多学科专业交叉渗透的综合技术。它涉及到通信基础理论（如数字通信技术），微波技术（如光纤信道的电磁场分析）以及电路设计与微电子技术（如ASIC专用集成电路）等。因此，无论是系

10、统的规划与设计，还是新型传输系统与体制的探索与研究，都要遇到冗长繁杂的计算。此外，为了验证其性能是否合科要求，还需反复进行实验研究与测试。如果每次都直接用真实系统进行实验，不仅耗资昂贵，费工费时，有时甚至难于找到问题症结所在，因此，解决上述问题的有效方法是采用计算机仿真技术，即通过建立器件部件乃至系统的模型，并用模型在计算机上做实验，利用计算机的高速运算处理能力，完成对光纤通信设备与系统的分析、设计以及性能优化与评估测试。2.1 光纤通信系统仿真软件的现状 仿真分为电路仿真和系统级仿真。电路级仿真就是由电阻、电容、电感等组成等效的电路模型来模拟器件的外特性。系统级仿真是肜传输函数或数字公式来模

11、拟器件的外特性的模拟。国外已有一些光纤通信系统仿真软件，用于电路分析时，其侧重点不同，例如Boss是一种界面友好的光链路仿真软件，它包括光纤器件模型，但只适用于单一波长系统。SCOPE（Super Co-mpact Optoelectronic Simulation）是一种把系统的光电器件和光器件用两端口网络模型来模拟的非线性微波仿真软件，其主要用途是对在微波频率的IM/DD光通信系统进行仿真。DEX SOLUS（Simulation of Light Using Spice）是基于Spice电路仿真软件的专用于光通信领域的信号分析软件，它采用等效电路模型来模拟光电器件，这些模型的光功率在仿真

12、中用电压来表征。还有其它电路级的仿真软件如iSMILE和MISIM等。IBM的OLAP（Optical Link Analysis Program）是一个把SYSTID和低级的光器件仿真软件综合起来应用的软件。还有一些新的仿真软件如iFROST（illinois FibeR-optic and Optoelectronic Systems Toolkit）等，用户可调用其他仿真软件来提供混合级的仿真环境。3 常用通信接口技术的探讨3.1与串并行转换器相连的光电器件在高速光纤通信系统中，传输的数据流需要进行格式转换，即在光纤传输时的串行格式及在电子处理时的并行格式之间转换。串行器-解串器(一般被

13、称作串并行转换器)就是用来实现这种转换的。串并行转换器与光电传感器间的接口通常为高速串行数据流，利用一种编码方案实现不同信令，这样可从数据恢复嵌入时钟。根据所支持的通信标准，该串行流可在1.25Gb/s(千兆以太网)、2.488Gb/s(OC-48/STM-16)、9.953Gb/s(OC-192/STM-64)或10.3Gb/s(10千兆以太网)条件下传输。3.2串并行转换器至成帧器接口在Sonet/SDH的世界中，光纤中的数据传输往往采用帧的形式。每帧包括附加信息(用于同步、误差监视、保护切换等)和有效载荷数据。传输设备必须在输出数据中加入帧的附加信息，接收设备则必须从帧中提取有效载荷数据

14、，并用帧的附加信息进行系统管理。这些操作都会在成帧器中完成。由于成帧器需要实现某些复杂的数字逻辑，因而决定了串并行转换器与成帧器间所用的接口技术，采用标准CMOS工艺制造的高集成度IC。目前的CMOS工艺不能支持10Gb/s串行数据流，因此串并行转换器与成帧器间需要并行接口。目前最流行的选择是由光网络互联论坛(Optical Internetworking Forum)开发的SFI-4，该接口使用两个速度达622Mb/s的16位并行数据流(每个方向一个)。SFI-4与目前很多新型接口一样，使用源同步时钟，即时钟信号与数据信号共同由传输器件传输。源同步时钟可显著降低时钟信号与数据信号间的偏移，但

15、它不能完全消除不匹配PCB线路长度引起的偏移效应。16个数据信号和时钟信号均使用IEEE-1593.6标准LVDS信令。该接口仅需在串并行转换器与成帧器间来回传输数据，距离较短，因此无须具备复杂的流控制或误差检测功能。力及对操作系统中电路板的可能损害。其二，在信号中嵌入时钟和数据的串行接口可完全避免时钟偏移问题。时钟偏移是PCB中数英寸长的并口所面临的主要问题。其三，串行信号的背板设计者还可提高传输速率，因为不存在时钟偏移，也就没有对未来性能的限制。被成功用作串行背板标准的接口是XAUI，它是为10千兆以太网开发的。该规范适用于通道排列电路，无论四通道轨线长度是否匹配，符合XAUI的器件均能接

16、收无误差数据。该接口使用差分电流模式逻辑信令，它还采用交流耦合模式，允许电路板间的参考电压不同。3.3 控制板接口已获得Motorola及Rapid IO贸易联合会支持的Rapid IO是使用交换架构实现点至点链接的接口。该接口的传输层规定数据如何封装在包中，每个包都具有数据源和目标信息，交换架构将数据包送往合适的目的地。Rapid IO在每个方向上提供8个或16个位，采用250MHz1.0GHz双数据速率。此外，串行Rapid IO可使用具有8b/10b编码的1通道或4通道数据，嵌入时钟达3.125Gb/s，它还具有CML差分信令。AMD及Hyper Transport联盟开发的Hyper

17、Transport使用通道器件实现点至点链接。数据以包的形式传输，每个包均包括数据源和目标信息。接收数据的通道器件按照数据包报头确定是将数据传至链中的下一个器件，还是直接处理数据。目前的Hyper Transport规范需要宽度为216位的并行数据。未来规范可支持更高速率。PMC-Sierra和Bro AD Com已经为Hyper Transport通信产品推出基于MIPS的处理器。PCI-SIG已经推出高速率PCI-X。它们使用与最初PCI-X相同的64位总线带宽，可支持双数据速率和四倍数据速率。PCI-X 533是速率最快的版本，最大总计带宽达34.1Gb/s。PCIX的传输通讯协议、讯号

18、和标准的接头格式都与PCI一并兼容，可以使3.3V的32位PCI适配卡可以用在PCI-X扩充槽上。当然如果你愿意，也可以将64位PCI-X适配卡接在32位PCI扩充槽上，不过，频宽速度将会大减。4 结束语目前，我国在光纤通信系统仿真研究方面已经起步，如清华大学、天津大学等均取得一些成绩，设计一个功能较强，性能可靠的光纤通信系统的仿真软件包，对适应光纤通信的飞速发展有着重要的理论意义和现实意义，具有较高的性价比和广泛的应用前景。Optical Fiber Communication System Simulation and Common Communication Interface Tech

19、nologyAbstractThis paper describes the development direction of optical fiber communications, described the characteristics of system simulation and development at home and abroad. The second part is commonly used by communication interface interface discussion.Keywords Opticalfibercommunications ,d

20、evelopment, SystemSimulation , Interface1 Outline1.1 Optical Fiber CommunicationIn the information superhighway concept was put forward after the optical fiber communication technology in increasing the capacity and extend the communication distance has made rapid development. Broadband fiber amplif

21、ier W-EDFA (Wide band Erbium-Doped Fiber Amplifier) and dense wavelength division multiplexing optical fiber communication technology development is the most eye-catching direction. Loss and dispersion in order to reduce the design of the dispersion shifted fiber DSF (Dispersion Shifted Fiber), in t

22、he 1525-1565nm band, the dispersion fell to -2 - +3 ps / (nm km) between; zero dispersion at 1540nm. DWDM systems to reduce four-wave mixing effect, but also designed a new type of non-zero dispersion fiber NZDF (Non-Zero Dispersion Fiber). At the same time, integrated opto-electronics technologies

23、(OEIC) is the rapid development of vertical-cavity surface-emitting laser VCSEL (Vertical Ca-vity Surface Emitting Laser) and electro-optical receiver optoelectronic integration has been achieved. Around a variety of light (OTDM) At present, there are active in research units.Optical fiber is used b

24、y many telecommunications companies to transmit telephone signals, Internet communication, and cable television signals. Due to much lower attenuation and interference, optical fiber has large advantages over existing copper wire in long-distance and high-demand applications. However, infrastructure

25、 development within cities was relatively difficult and time-consuming, and fiber-optic systems were complex and expensive to install and operate. Due to these difficulties, fiber-optic communication systems have primarily been installed in long-distance applications, where they can be used to their

26、 full transmission capacity, offsetting the increased cost. Since 2000, the prices for fiber-optic communications have dropped considerably. The price for rolling out fiber to the home has currently become more cost-effective than that of rolling out a copper based network. Prices have dropped to $8

27、50 per subscriber in the US and lower in countries like The Netherlands, where digging costs are low.Since 1990, when optical-amplification systems became commercially available, the telecommunications industry has laid a vast network of intercity and transoceanic fiber communication lines. By 2002,

28、 an intercontinental network of 250,000 km of submarine communications cablewith a capacity of 2.56 Tb/s was completed, and although specific network capacities are privileged information, telecommunications investment reports indicate that network capacity has increased dramatically since 2004.1.2

29、The history of fiber-optic communications In 1966 Charles K. Kao and George hockom proposed optical fibers at STC Laboratories (STL) at Harlow, England, when they showed that the losses of 1000 dB/km in existing glass (compared to 5-10 db/km in coaxial cable) was due to contaminants, which could pot

30、entially be removed.Optical fiber was successfully developed in 1970 by Corning Glass Works, with attenuation low enough for communication purposes (about 20dB/km), and at the same time GaAs semiconductor lasers were developed that were compact and therefore suitable for transmitting light through f

31、iber optic cables for long distances.After a period of research starting from 1975, the first commercial fiber-optic communications system was developed, which operated at a wavelength around 0.8 m and used GaAs semiconductor lasers. This first-generation system operated at a bit rate of 45Mbps with

32、 repeater spacing of up to 10km. Soon on 22 April, 1977, General Telephone and Electronics sent the first live telephone traffic through fiber optics at a 6 Mbit/s throughput in Long Beach, California.The second generation of fiber-optic communication was developed for commercial use in the early 19

33、80s, operated at 1.3 m, and used InGaAsP semiconductor lasers. Although these systems were initially limited by dispersion, in 1981 the single-mode fiber was revealed to greatly improve system performance. By 1987, these systems were operating at bit rates of up to 1.7 Gb/s with repeater spacing up

34、to 50km.The first transatlantic telephone cable to use optical fiber was TAT-8, based on Desurvire optimized laser amplification technology. It went into operation in 1988.Third-generation fiber-optic systems operated at 1.55 m and had losses of about 0.2dB/km. They achieved this despite earlier dif

35、ficulties with pulse-spreading at that wavelength using conventional InGaAsP semiconductor lasers. Scientists overcame this difficulty by using dispersion-shifted fibers designed to have minimal dispersion at 1.55 m or by limiting the laser spectrum to a single longitudinal mode. These developments

36、eventually allowed third-generation systems to operate commercially at 2.5 Gbit/s with repeater spacing in excess of 100km.The fourth generation of fiber-optic communication systems used optical amplification to reduce the need for repeaters and wavelength-division multiplexing to increase data capa

37、city. These two improvements caused a revolution that resulted in the doubling of system capacity every 6 months starting in 1992 until a bit rate of 10 Tb/s was reached by 2001. Recently, bit-rates of up to 14 Tbit/s have been reached over a single 160km line using optical amplifiers.The focus of d

38、evelopment for the fifth generation of fiber-optic communications is on extending the wavelength range over which a WDM system can operate. The conventional wavelength window, known as the C band, covers the wavelength range 1.53-1.57 m, and the new dry fiber has a low-loss window promising an exten

39、sion of that range to 1.30-1.65 m. Other developments include the concept of “optical solitons, “ pulses that preserve their shape by counteracting the effects of dispersion with the nonlinear effectsof the fiber by using pulses of a specific shape.In the late 1990s through 2000, industry promoters,

40、 and research companies such as KMI and RHK predicted vast increases in demand for communications bandwidth due to increased use of the Internet, and commercialization of various bandwidth-intensive consumer services, such as video on demand .Internet protocoldata traffic was increasing exponentiall

41、y, at a faster rate than integrated circuit complexity had increased under Moores Law. From the bust of the dot-com bubble through 2006, however, the main trend in the industry has been consolidation of firms and offshoring of manufacturing to reduce costs. Recently, companies such as Verizon and AT

42、&T have taken advantage of fiber-optic communications to deliver a variety of high-throughput data and broadband services to consumers homes.1.3 System SimulationSystem simulation is developed in the last two decades a science and emerging technologies. Is the so-called computer simulation model on

43、the computer system for experimental study of the actual process. The use of computer simulation can be repeated simulation of the same phenomenon of the objective world and thus to find out the inherent laws. In particular, contain random variables and random process, it is difficult to establish a

44、 mathematical model of an objective study of things, the computer simulation method has obvious advantages, has become the analysis, research and design of an important means of various systems. The application of computer simulation technology to the field of communications is one of an important b

45、ranch. With the development of communication technologies, communications networks, the number and complexity of the rapid growth of the design of communication systems in use of computer simulation technology has become a new system designed to shorten the design cycle and improve design reliabilit

46、y and improved system performance has been an indispensable tool.2 Optical fiber communication system simulationOptical fiber communication technology is more than one cross-discipline integrated technology penetration. It involves the basic theory of communication (such as digital communication tec

47、hnology), and microwave technologies (such as fiber channel analysis of electromagnetic fields), as well as circuit design and microelectronic technology (such as application specific integrated circuit ASIC) and so on. Therefore, whether it is systematic planning and design, or a new type of transm

48、ission system and the system of exploration and research, have experienced lengthy complicated calculations. In addition, in order to verify whether the performance requirements of Section need to research and experiment repeated testing. If every time the direct use of the real system experiments,

49、not only the cost of expensive, labor-and time-consuming and sometimes difficult to find the crux of the problem, therefore, address these problems is an effective means of computer simulation techniques, namely through the establishment of device components and the system model , and model experiments on the computer, using high-speed computer processing capacity, completion of the fiber-optic communications equipment and systems