电子信息工程外文翻译综合布线的未来.DOC

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1、外文文献及译文文献、资料题目:The future of structure cabling systems外文文献： The future of structured cabling systemsWhich technologies will meet speed and data-transmission requirements in the future?To discuss the future of structured cabling systems, we should spend a moment looking at the past and present practi

2、ces. Before early 1984, communications wiring systems, as they were then called, were not topics of much discussion. Data-transport speeds were comparatively slow, transmission bandwidth requirements were minimal, and others provided the design and installation of the cabling system. The telephone c

3、ompanies took care of the installation and maintenance of the telephone service. When data services became distributed, the cabling system was vendor-specific, and the installation and maintenance of the cable plant was provided by the equipment vendors, or specialized independent contractors.In Jan

4、uary 1984, the courts in the U.S. made several important rulings that changed the way telecommunications was provided and distributed. Outside of traditional suppliers of cabling systems, not much was understood about the cabling requirements for communications transport. The proliferation of media

5、and connector interfaces, a lack of standard transmission specifications, and the introduction of cabling schemes by vendors added to the users confusion. Bringing order to the confusion and creating generic cabling systems demanded the creation of a standards body whose output would focus on commer

6、cial buildings and communications cabling.Since the introduction of the first cabling standard in1991 by the Telecommunications Industry Association/Electronic Industry Alliance (TIA/EIA), that same group has issued a series of standards and specifications regarding most aspects of the structured ca

7、bling systems. These standards have provided guidance related to evolving high-speed information transport systems. The vast majority of past and present digital communications, used in the commercial world, has been transported on unshielded twisted-pair (UTP) cabling systems. UTP became the medium

8、 of choice because it was economical, perfectly adequate for the applications, and comparatively easy to install versus other available media types.With advancements in network speeds, new transmission specifications for UTP cable and connecting hardware have been promoted by manufacturers and event

9、ually endorsed by the standards community. In 1991, the highest rated bandwidth over UTP was 16 MHz; we are now faced with transport speeds demanding transmission bandwidths of 250MHz and beyond. Manufacturers have risen to the challenge and provided UTP components for todays transmission requiremen

10、ts in excess of 600 MHz. What media and connectors will be available that will be economically feasible at bandwidths of 1G MHz? At what point does UTP become less easy to use and less economical than other media?Future directionsAs far as we can see into the future, commercial information transfer

11、will consist of both low-speed and high-speed requirements. Applications such as voice, building automation systems, alarms, and security systems will still use low bandwidths. Voice information may change from central office exchange delivery to intelligent peripheral, but bandwidth requirements wo

12、nt increase by a large amount. The data packets, with which the voice packets ride, will increase bandwidth requirements. The requirements to transport large amounts of information in shorter and shorter periods of time are changing, and will continue to change. Applications such as graphical data (

13、both schematic and pictorial), scientific modeling, desktop videoconferencing, multi-tiered relational databases and other data-intensive information will drive up the bandwidth requirements.If history is any predictor of the future, we will see information transfer speeds increase at least one orde

14、r of magnitude per decade. We have seen local area network speeds, on UTP, increase from 10 Mb/s in the mid 1980s to 100 Mb/s in the mid 1990s then to 1 Gb/s in the late 1990s. Today, standards are being written for 10 Gb/s. Where will we be in 2010 or 2020? Microsofts Bill Gates is quoted as saying

15、, We will have infinite bandwidth in a decades time. Lawrence Berkeley Laboratory (Berkeley, CA) has projected its throughput needs for 2020 to be 40 Gb/s. What will be its media of choice: UTP, coaxial, shielded twisted-pair, optical fiber, or wireless technology?The two major properties required f

16、or any cabling system to be the system of choice are its performance and its relative economics (which include ease of installation). Undoubtedly, fiber and shielded twisted-pair (STP) systems are quite robust and provide greater signal headroom than UTP. However, they lag far behind UTP in customer

17、 acceptance for todays applications. But will UTP and other media systems provide the bandwidth for future applications? Will they provide economical solutions? Lets look at the proposed solutions for future requirements. Unshielded twisted-pairCurrently, standards are being solidified to extend the

18、 transmission characterization of UTP to 250 MHz. Many manufacturers are advertising the availability of products that exceed yet-to-be-ratified specifications. Many technical hurdles have to be solved before a Category 6 standard is published. However, it is reasonable to expect that these hurdles

19、- both technical and political - will be resolved. It is generally recognized that UTP has not yet been pushed to its theoretical limits. The question yet remains as to the continued viability of UTP as information speeds increase.If future technology does not improve the efficiency of band-width ut

20、ilization, then the cost of the electronics, installation detail, and the testing requirements may diminish UTPs benefits relative to other potential options. It should be noted that currently, there are no plans to develop a standard copper solution for 10 Gigabit Ethernet.Shielded twisted-pair Shi

21、elded twisted-pair is currently characterized at frequencies to 300 MHz. The International Organization for Standardization and International Electro-technical Commission (ISO/IEC-Geneva, Switzerland) is now studying STP for potential publication as a Category 7 standard. The spectral bandwidth will

22、 be characterized at frequencies to 600 MHz. Despite being an exception ally good transmission medium, its material and installation costs have restricted its use to special situations and certain countries. Undoubtedly, STPs bandwidth limitations have not yet been reached, but as is the case with U

23、TP, economics could be the major stumbling block to its adaptation. The installation of STP requires highly trained installers. North American industry experts doubt that end users or installation contractors will be quick to embrace STP. Fiber-optic WDM Wave division multiplexing (WDM) is a new tec

24、hnology that expands the data-carrying capacity of optical fiber rather than using a new media type for structured cabling systems. To increase the carrying capacity of fiber, the laser light that carries data through fiber-optic glass can be split into different colors, or more precisely, wavelengt

25、hs, each of which carries a discrete data channel. Today, the technology will support up to 40 different wavelengths. In the near future, 128 channels will be available. The best result of this technological development is that transmission facilities for new wavelengths can be retrofitted onto exis

26、ting plants that connect to fiber already in the ground, which makes it the easiest way to increase bandwidth. This technology will obviate the requirements of additional fiber and will use the existing optical fiber and connectors. Plastic optical fiberHistorically, plastic optical fiber (POF) has

27、been relegated to low-speed, short-distance applications. Recent technical developments of graded-indexed POF have increased bandwidths to 3 GHz/100 meters. But this medium is not endorsed by any standards body because the current technology is limited to a distance of 50 meters at the required band

28、width. Endorsement within a written standard is crucial for market acceptance. It will be perhaps five years before low-cost POF will be commercially available. If and when a standards body sanctions POF, it should offer a more robust system for applications currently served by copper media, at a co

29、st below that of glass optical fiber. Wireless technology Much has been written about the prospect of wireless networking replacing fixed-media structured cabling systems in the future. Currently, cost and low bandwidth have left wireless technology with approximately 1% of the number of deployed Et

30、hernet ports. The features of wireless networking are beguiling to those who are involved with the design, installation, and maintenance of structured cabling systems. With wireless, there are no more concerns about running cable to inaccessible locations, and no more concerns about cable types. But

31、 for all the magic of wireless networking, there are downsides. Although a standard for wireless networking exists - IEEE 802.11b put out by the Institute of Electrical and Electronics Engineers - complete interoperability among all WLAN vendors remains unattained. IEEE 802.11b stipulates an 11Mb/s

32、data-transfer rate. An Australian company has recently developed a wireless system that claims to support 54Mb/s. In an open office plan, propagation of the radio waves may be limited to distances of 200 feet to 500 feet. In a closed-wall office environment, propagation may be limited to as little a

33、s 100 feet. Undoubtedly, the cost of wireless networking will be reduced and the bandwidth will increase. Wireless networking can serve admirably in numerous applications. Coaxial Coaxial cable has been the medium of choice for wideband applications ranging from high-fidelity audio to television to

34、baseband and broadband communications. Coaxial cable was the primary media for 10-Base-5 and 10-Base-2 Ethernet. The advent of higher-bandwidth UTP cable and connector technology replaced coaxial cable in commercial networks and has relegated its primary use to legacy networks and cable television.

35、Cost considerations Numbers being what they are, one cannot just look at the cost of materials when making a purchasing decision. The applications to be run and the anticipated requirements must be factored into any decision. For instance, Category 5 cable is characterized at frequencies to 100 MHz,

36、 while Category 6 is characterized at 21/2 times bandwidth. Trying to double the bit rate of a signal using the same bandwidth will considerably increase electronics costs, as it will take more-sophisticated equipment to decipher the transmitted signal. Unless there is a need to reduce electromagnet

37、ic interference (EMI), most users cannot justify the up to 300% price premium of STP over UTP. The use of fiber, at 4 to 41/2 times the cost of UTP, may be justified on several levels: EMI cancellation, increased bandwidth, and longer distances. Shielded twisted-pair and screened twisted-pair media

38、will also continue to find their use in high-EMI environments for a long time to come. Their cost premium and increased installation costs are a disadvantage, but they offer solid performance at frequencies higher than those that UTP can accommodate. Wireless technology will undoubtedly advance and

39、continue to support greater bandwidth requirements. It will probably see an even greater share of the market, especially in residential environments. Users should be interested in the information-transfer system as a tool to provide productivity for their enterprise, rather than support one technolo

40、gy versus another technology. And, even though in terms of application protocol Gigabit Ethernet will be with us for awhile, and Category 5E and Category 6 will support it just fine, we do know that in the next 5 to 10 years, 10-Gigabit Ethernet will require a totally optical-fiber infrastructure. D

41、ebate continues on employing the new multimode fiber versus single mode fiber, short wavelength (SX) versus long wavelength (LX) transmission, and using WDM for new fiber installations. The development of a 1,300nm VCSEL will enhance single mode fibers chance of deployment in both backbone and horiz

42、ontal usage. It seems that the ultimate solution will probably be a combination of many of the current optical-fiber options. In the final analysis, manufacturers of structured cabling products must always be aware of new developments in electronic components, breakthroughs in materials technology,

43、and innovations in signal transmission. They must also be cognizant of all new application protocols being developed. Lloyd Mariner is chief operating officer of Molex Premise Networks (Hudson, NH). 中文译文：综合布线的未来哪种技术将会满足未来对速度和数据传输的要求？讨论未来的综合布线系统，我们应该花一点时间去回顾过去和现在的做法。在1984年初，当时被称为通信布线系统，并没有被过多的讨论。和其他区

44、各种布线系统相比，数据传输速率低，对传输带宽的要求是很小的。电话公司只负责电话的安装和维修服务。当数据服务成为分散式的，有负责布线系统的厂商，有负责安装及维修电缆的设备厂商，或专门的独立承包商。在1984年1月，美国的法院颁布的几个重要裁决改变了电信业务的提供和分配结构。传统的综合布线系统供应商，他们不太了解综合布线对传输的需求。多媒体扩展连接接口缺乏标准传输规范，厂商介绍的各种布线方案给使用者造成了许多混乱。为了消除这些混乱就需要创建一种专注于商业大楼并有统一输出标准的通用布线系统。自从1991年电信行业协会/电子工业联盟，共同发表了一系列关于综合布线系统的标准和规范。一些组织也对综合布线的

45、各个方面发布了一系列的标准和规范。这些标准有助于发展高速传输系统。用于商业界的绝大部分的过去和现在的数字通信系统，都已运用非屏蔽双绞线。之所以双绞线成为新选择的媒介，是因为它经济，非常适合应用，且相对易于安装与其他现有的媒体设备。随着网络速度的提升，制造商研发了双绞线和硬件接口技术，并促使标准化组织最终认可了这些标准。1991年双绞线的最高带宽是16MHz，现在面临的是带宽超过250MHz及以上的要求。制造商已经开始研发带宽超过600MHz的双绞线。什么样的媒介和适配器能用较少的花费达到超过1GHz的带宽？为什么双绞线的经济性已不如其它媒介？新的方向在我们能预见的未来里，商业信息的传递包括低速

46、和高速两种要求。仍继续使用低带宽的领域如，楼宇自控系统，报警系统及安全防范系统。语音信息可以从中央办公室传递到智能外设，但并不需要增加带宽。数据包，其中包括语音数据包，将增加带宽的要求。在越来越短的时间内传输大量信息的需求正在增加，并将继续扩大。一些应用如，图形数据（包括原理图和图案），科学建模，桌面视频会议，多层次的关系数据库及其他数据密集的信息会有提高带宽的需求。如果未来是可以预测的，我们将看到信息的传递速度每十年至少提高一个数量级。我们已经看到局域网的传输速度已从80年代中期的10Mb/s提高到了90年代中期的100Mb/s和90年代末的1Gb/s，如今已超过了10Gb/s。那么到201

47、0年或2020年那？正如微软的比尔盖茨说过的“我们在10年内将有无限的带宽”。劳伦斯伯克利实验室预测到2020传输速度将达到40Gb/s。要达到如此高的速度应选择哪种传输介质呢？是双绞线，电缆，屏蔽双绞线，光纤还是无线技术？系统性能和经济性是挑选布线系统的两项重要依据。毫无疑问，光纤和屏蔽双绞线比非屏蔽双绞线传输的信息量更大。然而它们远远落后于非屏蔽双绞线在实际当中的应用。但非屏蔽双绞线能满足未来的需求吗？让我们看看有哪些方案可以解决这些问题。非屏蔽双绞线目前，非屏蔽双绞线的传输速度已达到250MHz。许多厂家都宣称其产品性能都超过了现有的标准。在六类标准出台之前，许多技术障碍都没有得到解决。

48、但可以相信这些障碍，无论是技术方面的还是政治方面的，都会得到解决。人们普遍认为，非屏蔽双绞线的传输速率还尚未达到极限。非屏蔽双绞线的持续有效性能否跟随信息传输速率一起提高仍然是一个问题。如果未来的技术并不能提高带宽利用效率，那么电子产品的成本，安装详图及测试需求成本的可能会减少双绞线的优点相对于其它潜在的媒介。应该指出的是，目前还有没有计划制定一个标准的万兆以太网。屏蔽双绞线屏蔽双绞线的特点是其频率目前在300MHz。国际标准化组织和国际电工委员会正在研究7类标准。其特点是光谱带宽的频率在600MHz。尽管屏蔽双绞线是一个良好的传输媒介，但原材料和安装费用较高，限制了其使用。毫无疑问，屏蔽双绞

49、线还尚未达到传输极限。但相对于非屏蔽双绞线，屏蔽双绞线的花费较高是它的一个主要缺点。同时它还需要训练有素的安装人员。但北美的一些专家认为，用户和工程承包商最终都会采用屏蔽双绞线。光纤波分复用光纤波分复用是一种新兴的技术。光纤利用波分复用技术扩展了数据的传输能力，而不是为综合布线系统从新选用一个传输媒介。为了提高光纤的承载能力，携带数据的激光通过光纤玻璃时可以被分成不同的颜色，或者更准确地称为波长，每个波长都是离散数据通道。今天，该技术已支持多达40个不同的波长。在不久的将来，可达到128通道。这一技术发展最好的结果是，一个新波长可以耦合到光线路的同一根光纤中进行传输。这样可以很容易的增加带宽。这项技术可没有额外的要求，利用现有的光纤连接器即可。塑料光纤纵观历史，塑料光纤已被应用到低速，短距离的传输系统当中。最新的技术已将塑料光纤的传输速度增加到了3GHz。但是塑料光纤并不被所有的机构所认可，原因是当前的技术仅局限于50米的传输距离。如今的市场只接受有书面认可的产品，而且低成本的塑料光纤也不会被市场接受