| 摘要 |
<p>Title "Improvements in or relating to graded index optical fibers" Graded index optical fibres can be made by a double crucible technique in which the refractive index gradation is induced by thermal diffusion. In fibre made from alkali-boro-alkaline earth-silica glasses, the refractive index variation in the fibre is improved if the core and cladding glass compositions are selected so that no simple ion-exchange processes occur. These fibres have improved bandwidth. Preferred glass compositions for the core contain 55-65 mole per cent silica, 10-20 mole per cent boric oxide, 14-25 mole per cent sodium oxide, and up to 20 mole per cent of alkaline earth oxide, preferred glass compositions for the cladding contain 55-65 mole per cent silica, 10-20 mole per cent boric oxide, 19-25 mole per cent sodium oxide, and the cladding glass contains the same amount or less sodium oxide than the core.</p> |
