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

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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.【C1】H __________, fiber optics was already a well-established commercial technology when the famous paper by Kao and Hockham, 【C2】__________(claim) the use of low-loss optical fibers for communication, appeared in 1966.The first low-loss silica fiber was described in 【C3】__________which appeared in October of 1970.The date of this publication is sometimes 【C4】__________(cite) as the beginning of the era of fiber communication.Although this development did receive 【C5】__________(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 【C6】wh__________ these fiber components could ever be produced economically enough, but the market potential was very significant.【C7】__________(consequence), research and development activity expanded rapidly, and a number of important issues were 【C8】 re__________ during the early 1970s.During the middle and late 1970s, the rate of progress towards marketable products accelerated as the emphasis 【C9】__________(shift) from research to engineering.Fibers with losses 【C10】app__________ the Rayleigh limit of 2 dB/km at a wavelength of 0.8μm were produced.
      By 1980 improvement in component performance, cost, and reliability led to major commitments on the part of telephone companies. [br] 【C10】

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答案 approaching

解析 approaching the Rayleigh limit接近瑞利极限。

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