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  3. In the early 1950s the researchers who produced the first clad glass optical

In the early 1950s the researchers who produced the first clad glass optical

游客2023-10-18  67
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. [br]
选项
答案 approaching
解析 approaching the Rayleigh limit接近瑞利极限。
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