伪劣商品U12
Passage 2
初一数学计算题100道 Optical Communications
光学通讯
Important steps have been taken since 1974 toward finding major applications for optical fibers in communications.
自从1974年以来，已经采取了一些重大的措施来发展光学纤维在通讯方面的应用。
The u of radio optics for communication through the atmosphere and in space will continue to grow in importance, particularly with the development of space systems and technology, but the prospect of developing lightwave communications systems to compete with and expand traditional communications rvices has shifted the emphasis toward the u of light-wave-guiding fibers. Experimental optical-fiber transmission systems are already in u in some of the telephone systems in a few countries.
无线电光学在大气和空间通讯中的应用，特别是随着航天空间系统和技术的发展将显得越来越重要。但是，从发展光波通讯系统，以便与传统的通讯业务抗衡并扩大传统的通讯业务的前景来看，重点已经移向光导纤维的应用了。目前，试验性的光学纤维发送系统已经在一些国家的电话系统中使用。
怎么拉人进群 The success of industry in turning such effective techniques to advantage by developing low-cost products will determine the impact which optical fibers have on communications.
必须研制出廉价的产品，才能更有利于运用这种高效能的技术，其成功将决定光学纤维对通讯产生影响有多大。
The telephone system can be divided into three networks: the local network, which ties customers to their respective local switching offices; the trunk network, which interconnects the switching offices; and the long-distance network between cities.
电话通讯网可分三类：市内电话网，中继局电话网和长途电话网。市内电话网把用户分别和其当地的中继电话局连接起来；中继局电话网把各中继电话局相互连接起来；长途电话网则把各城市连接起来。
Local lines,traditionally called loops, tie customers to switching offices almost on a one-to-one basis; large, relatively short groups of lines tie the switching offices together; and even larger and much longer groups of lines interconnect cities.
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市内电话线传统称作环路，几乎是在一对一的基础上把用户和中继电话局连接起来。大型的和较短途的各组线路把各中继电话局连接起来。那些更大型，更长得多的各组线路则把各个城市相互连接起来。
Even though optical fibers are much smaller than wire pairs, and silica (the most widely ud material in fibers) is vastly more abundant than copper, the cost of preparing the rods from which optical fibers are drawn is veral times greater than the cost of producing wires.Moreover, studies suggest that this may be the ca for some time.
尽管光学纤维比电话线要细的多，二氧化硅（光学纤维中用的最广泛的材料）的来源也比铜丰富得多，但是用于接出光学纤维的二氧化硅棒的制造成本却要比生产铜线的成本高好几倍。而且，一些研究结果表明，这一情况或许会继续一段时间。
However, fiber systems can carry so many more telephone conversations at the same time than wire pairs and can carry them so much farther without amplification or regeneration, that when there are many telephone calls to be carried between points such as switching offices, fiber systems are economically attractive. Thus the interoffice trunk network will be the first to benefit from this new technology.
然而，光学纤维系统能同时传递比一般电话线更多的电话通话，并且不用放大或再生就能传递到更远得多的距离，因此当各地之间（例如各中继局之间）需要进行大量的通话时，光学纤维通讯系统从经济角度来说就更具有吸引力。因此局间中继电话网将首先从这种科技术中得到好处。
In fact, various trunk-oriented communications systems are under construction or in operation in many industrialized countries.
事实上，许多工业化国家已经在建造或使用各种以中继电话网为重点的通话系统。
Optical fibers are also being considered for the intercity network. Competition is more dif
ficult, though, with existing high-capacity systems that u coaxial transmission lines,waveguide, microwave radio, and satellites.
目前，供城市间电话网使用的光学纤维通讯系统也正在考虑之中。虽然光学纤维通讯系统要和现有的大容量通讯系统，如同轴传输线路，波导管，微波无线电和卫星等，进行竞争还比较困难。
Larger fiber bandwidth, lower loss, and more reliable optical sources would make optical fibers more competitive in this ctor. As the characteristics are improved, optical fibers will most likely be ud for undera cable systems as well.
糖拌西红柿 但是，由于光学纤维频带较宽，能量损耗较少，光源较稳定可靠，因此在这一领域中会有更大的竞争能力。随着这些特性的改进，光导纤维也非常可能用于海底电缆系统。
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