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  3. In the early 1950s the researchers who produced the first clad glass optical fibers were not thinking of using them for communic

In the early 1950s the researchers who produced the first clad glass optical fibers were not thinking of using them for communic

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问题     In the early 1950s the researchers who produced the first clad glass optical fibers were not thinking of using them for communications.【46】H______, fiber optics was already a well-established commercial technology when the famous paper by Kao and Hockham,【47】______ (claim) the use of low-loss optical fibers for communication, appeared in 1966. The first low-loss silica fiber was described in【48】______which appeared in October of 1970. The date of this publication is sometimes【49】______(cite) as the beginning of the era of fiber communication. Although this development did receive【50】______ (consider) attention in the research community at the time, it was far from inevitable that a major industry would evolve.
    The technological barriers appeared formidable because there were serious doubts as to【51】 wh______these fiber components could ever be produced economically enough, but the market potential was very significant.【52】______(consequence) , research and development activity expanded rapidly, and a number of important issues were【53】re______during the early 1970s. During the middle and late 1970s, the rate of progress towards marketable products accelerated as the emphasis【54】______(shift) from research to engineering. Fibers with losses【55】app______the Rayleigh limit of 2 dB/km at a wavelength of 0. 8 μm were produced.
    By 1980 improvement in component performance, cost, and reliability led to major commitments on the part of telephone companies.
选项
答案approaching
解析 approaching the Rayleigh limit接近瑞利极限。
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C类竞赛（非英语专业本科）

大学生英语竞赛（NECCS）

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