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1、Modern Communications,http:/,大连理工大学出版社,Unit 5,机 电 英 语,Contents,Part Passage A,从1974年发现光纤在通讯中的重要应用以来，通讯事业得到了长足的发展。随着空间系统和技术的发展，通过大气和空间进行无线光学通讯将是持续发展的重点。,Optical Communications,Important steps have been taken since 1974 toward finding major applications for optical fibers in communications.,随着空间系统和技术的
2、发展,通过大气和空间进行无线光学通讯将仍旧是发展的重点with 引导的介词短语作状语,可译为:“随着的发展” 例如:With the development of economy, peoples life is becoming better and better. 随着经济的发展,人们的生活越来越好,With the development of space systems and technology, the use of radio optics for communications through the atmosphere and in space will continue
3、to grow in importance.1,Part Passage A,But the prospect of developing light-wave communications systems to compete with and expand traditional communications services has shifted the emphasis toward the use of light-wave-guiding fibers. Experimental optical-fiber transmission systems are already in
4、use in some of the telephone systems in a few countries.,但是光波通讯系统与传统通信服务系统之间的竞争和扩展的重点已经转移到利用光导纤维。实验性的光纤传输系统已经在几个国家的电话系统中使用。,Optical Communications,Part Passage A,The success of industry in turning such effective techniques to advantage by developing low-cost products will determine the impact which
5、optical fibers have on communications.,借助发展低成本产品，把实用技术成功转变成工业生产将决定光学纤维在通讯中的影响。,Optical Communications,Part Passage A,The telephone systems can be divided into three networks: the local network, which ties customers to their respective local switching offices; the trunk network, which interconnects t
6、he switching offices; and the long-distance network between cities.,电话系统可分为三个网络：当地网，连接客户与当地的中继局；中继网，连接各中继局以及城市之间的远程网；,Optical Communications,Part Passage A,large, relatively short groups of lines tie the switching offices together; and even larger and much longer groups of lines interconnect cities.
7、,本地线路，通常称环路，连接用户与中继局，大都建立在一对一的的基础上，大的、短粗线路把各中继局连在一起，更大、更长的组线实现城市互连。,Optical Communications,本地线路,通常称环路,连接用户与中继局,大都建立在一对一的基础上 called 是过去分词作定语,修饰local lines ,译为:“本地线路,通常称环路”在这里可以转化为非限制性定语从句which are traditionally called loops 例如:I have been to Changchun called an Automobile City in China. 我去过被称为中国汽车城的长
8、春,Local lines, traditionally called loops, tie customers to switching offices almost on a one-|to-one-basis;2,Part Passage A,Even though optical fibers are much smaller than wire pairs, and silica (the most widely used material in fibers ) is vastly more abundant than copper, the cost of preparing t
9、he rods from which optical fibers are drawn is several times greater than the cost of producing wires. Moreover, studies suggest that this may be the case for some time.,尽管光学纤维比金属线对要细，并且二氧化硅（纤维中广泛使用的材料）比铜丰富的多，但是制造光纤的代价却是生产通讯线的好几倍。而且，研究者们认为这种情况还将持续一段时间。,Optical Communications,Part Passage A,However,
10、fiber systems can carry so much more telephone conversations at the same time than wire pairs, and can carry them so much farther without amplification of regeneration, that when there are many telephone calls to be carried between points such as switching offices, fiber systems are economically att
11、ractive.,然而，光纤系统同时可容纳比金属线对多得多的电话线路，并且在不需要放大的情况下把信号送得更远。在两点之间，比如中继局有很多电话要呼叫要传送的时候，光纤系统就是特别经济的。,Optical Communications,Part Passage A,Thus the interoffice trunk network will be the first to benefit from this new technology. In fact, various trunk-oriented communications systems are under construction
12、or in operation in many industrialized countries.,所以，局间的中继网是最先受益于这种新技术的。 事实上，在许多工业化国家，各种与中继有关的通信系统正在建设或已经运行。,Optical Communications,Part Passage A,Optical fibers are also being considered for the inter-city network. Competition is more difficult, though, with existing high-capacity systems that use
13、coaxial transmission lines, wave-guide microwave radio and satellites.,光学纤维也被用于城市互联网。虽然存在同轴传输线、波导微波无线电系统和卫星传输这些大容量系统，但是竞争仍然很激烈的。,Optical Communications,Part Passage A,Larger fiber bandwidth, lower loss, and more reliable optical sources would make optical fibers more competitive in this sector. As t
14、hese characteristics are improved, optical fibers will most likely be used for undersea cable systems as well.,宽带、低损耗、可靠性高使得光学纤维更具有竞争力。随着这些特性被加以改善，光学纤维最有可能被用于海底光缆系统。,Optical Communications,Part Passage A,虽然预测一些具体的细节比较困难，但还说不定有一天低损耗、宽频带的光学纤维系统在应用于当地电话系统时并不比铜线昂贵。那时，可以想象使用同一光纤的私人、当地两路电视服务系统将不再比一路电话系统贵。
15、,Optical Communications,虽然预测一些具体的细节比较困难,但也说不定有一天低损耗宽频带的光学纤维系统在应用于本地电话系统时并不比铜线昂贵多少那时,可以想象使用同一光纤的私人本地两路电视服务系统将不再比一路电话系统贵 although 引导的是让步状语从句,可译为:“虽然但是” 在“It is not unlikely that.”中it作为形式主语放在句首,真正的主语是that引导的主语从句not unlikely 是双重否定表肯定,译为:很有可能,Although it is difficult to predict the specific details, it i
16、s not unlikely that some-day low-loss, large-bandwidth optical fibers and the required special electronics may be hardly more expensive than copper wires for providing a local phone service. At that time it is conceivable that a private, local two-way television service using the same fibers may be almost as inexpensive as a telephone service.3,Part Passage A,A few optical fibers data link systems are
