2. 外语
  3. One of the most important technological developments during the 1980s has been the emergence of optical fiber communication as a

One of the most important technological developments during the 1980s has been the emergence of optical fiber communication as a

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问题 One of the most important technological developments during the 1980s has been the emergence of optical fiber communication as a major international industry. One indication of the(51)of this development is the total(52)of installed fiber, which was estimated to be 3.2 million kilometers in the U.S. alone by the end of 1987. Over 90% of this fiber was placed.(53)during the time period of 1982—1987. Long-haul trunk installations(长途干线设施) have dominated,(54)for about 95% of the fiber in the U.S.
    In the early 1950s the researchers who produced the first clad glass optical fibers were not (55)of using them. for communications. (56), fiber optics was already a well-established commercial technology when the famous paper by Kao and Hockham,(57)the use of low-loss optical fibers for communication, appeared in 1966.
   The first low-loss silica fiber was described in a publication which appeared in October of 1970. The date of this publication is sometimes(58)as the beginning of the era of fiber communication. Although this development did receive(59)attention in the research  community at- the time, it was far from inevitable that a major industry would evolve.
   The technological barriers appeared(60)because there were serious doubts as to(61)these fiber components could ever be produced economically enough, but the market potential was very significant. (62), research and development activity expanded rapidly, and a number of important issues were(63)during the early 1970s. During the middle and late 1970s, the rate of progress towards marketable products accelerated as the emphasis(64)from research to engineering. Fibers with losses approaching the Payleigh limit of 2 dB/km at a wavelength of 0.8um were produced.
    By 1980 improvement in component performance, cost, and reliability led to major commitments (65)the part of telephone companies.
选项 A、in bulk
B、in force
C、in practice
D、in service
答案D
解析 in bulk散装；大量；批发in service作帮工；在军中服役；在使用中；in practice实际上；在开业中；be in force生效，有效。此句可译为：90%以上的光纤都是在1982年到1987年间投入使用的。从上下文来看，此处指“投入使用”，故选D。
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