填空题.In the early 1950s the researchers who produced the first clad glass optical fibers were not thinking of using them for communications. H 1 , fiber optics was already a well-established commercial technology when the famous paper by Kao and Hockham, 2 (claim) the use of low-loss optical fibers for communication, appeared in 1966. The first low-loss silica fiber was described in 3 which appeared in October of 1970. The date of this publication is sometimes 4 (cite) as the beginning of the era of fiber communication. Although this development did receive 5 (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 wh 6 these fiber components could ever be produced economically enough, but the market potential was very significant. 7 (consequence), research and development activity expanded rapidly, and a number of important issues were re 8 during the early 1970s. During the middle and late 1970s, the rate of progress towards marketable products accelerated as the emphasis 9 (shift) from research to engineering. Fibers with losses app 10 the Rayleigh limit of 2dB/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.