Method and apparatus for manufacturing preform for fluoride glass fiber
AssigneeKokusai Denshin Denwa Kabushiki Kaisha
InventorsYoshinori Mimura, Osamu Shinbori, Tetsuya Nakai, Hideharu Tokiwa
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Abstract
A method and apparatus is disclosed which ensures highly accurate control of the core-cladding diameter, enabling the fabrication of a preform for the single mode fiber. Moreover, glass refining steps for dehydration, the removal of compound ions, the reduction of the absorption loss by transition metals, etc. and preform manufacturing steps are combined into a series of steps, and the entire manufacturing process can be mechanized and automatically controlled; therefore, the yield rate of product is high and the industrial-scale productivity is also excellent.
Claims11
A method of manufacturing a fluoride glass preform for drawing therefrom a fluoride glass optical fiber comprising, containing in a first crucible fluoride glass material for use as cladding on the optical fiber and containing a different fluoride glass material in a second crucible, containing the crucibles in a sealed vessel containing a fluorine-series gas charge as an atmosphere, melting the glass in the crucibles into two glass melts by application of heat simultaneously in a same temperature range over which no marked evaporation of glass components occurs and at which the fluorine-series gas reacts with oxides and compound ions contained in the glass so that impurities are decomposed and removed, cooling the melts to a same temperature and holding it without crystallizing the glass melts effectively raising the balances of transition metals contained in the melts to a level for reducing absorption losses in the optical fiber made therefrom, further cooling the melts to a same temperature, drawing glass from the melts concentrically as a rod having a core of said core glass and a cladding made of said cladding glass about said core, and cooling the rod to solidify it into said preform.
Apparatus for manufacturing a fluoride glass preform for drawing therefrom a fluoride glass optical fiber comprising, two crucibles for containing therein a fluoride glass material for use as cladding on the optical fiber to be drawn and a second crucible for containing a different fluoride glass material for use as a core of the optical to be drawn, a sealed container containing the two crucibles, means for introducing a fluorine-series gas into the sealed vessel for establishing an atmosphere in said sealed vessel, heating means for heating the two crucibles jointly in the sealed vessel at a same temperature rate to a same temperature level to develop two separate glass melts in the crucibles, means for drawing from the melts in the crucibles molten core glass concentrically with molten cladding glass about the core glass as a vertically descending rod defining the preform.
Dependencies are inferred from the claim text.