Method of preparing optical fibers of silica
AssigneeBell Telephone Laboratories, Incorporated
InventorsThomas Y. Kometani, Darwin L. Wood
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Abstract
A hydrolysis method of purifying silicon tetrachloride is shown that reduces losses in optical fibers made from silica produced therefrom. Water is added to impure liquid silicon tetrachloride, which forms a gel which is then separated from the remaining SiCl.sub.4. Metal impurities, OH-containing impurities, and SiHCl.sub.3 are removed by this process. In a preferred embodiment, the water is added by bubbling a wet gas through the SiCl.sub.4. A residual amount of OH containing impurities and HCl is left after the hydrolysis, which impurities may be further removed by a refluxing technique.
Claims6
A method of making an optical fiber by steps comprising oxidizing silicon tetrachloride to form silica, CHARACTERIZED by the additional step of purifying prior to oxidation impure liquid silicon tetrachloride by steps comprising adding water to said impure liquid silicon tetrachloride and separating the gel formed thereby from the remaining silicon tetrachloride, with the amount of the added water being less than 25 weight percent of said impure liquid silicon tetrachloride, and thereafter forming an optical fiber comprising silica produced by the oxidation of said remaining silicon tetrachloride, and
- further characterized in that said water is added in sufficient amount so that the concentration of OH-containing impurities in said remaining silicon tetrachloride is approximately 95 parts per million by weight.
The method of claim 14 FURTHER CHARACTERIZED by effecting said reducing the amount of OH-containing impurities and HCl by heating said remaining silicon tetrachloride to approximately its boiling point in a vessel having an opening, so that at least a portion of said remaining silicon tetrachloride condenses on the interior of said vessel.
Dependencies are inferred from the claim text.