Melt coating of tin on silica optical fiber

The coating of a silica optical fiber with molten tin metal is analyzed rig orously by developing a numerical method based on two- and three-dimensiona l (2- and 3-D) conduction models. In the analysis, the axial temperature di stribution in both the fiber and coating is obtained in terms of the depth of the melt and the fiber draw speed. A coating applicator has been designe d for tin (Sn) coating and fibers with a coating thickness from 5 to 20 mu m were fabricated with draw speeds ranging from 50-150 cm/s, The numerical model was found to be in agreement with the experimentally obtained results for various coating conditions and fiber drawing parameters. It is shown t hat for tin, a low-melting-point metal, the freezing takes place primarily within the coating applicator, As a result of the presence of this "subcoat ing," additional coating occurs as the fiber leaves the applicator. Since t his tin coating is hermetic, a mean failure strength of 8 GPa is measured f or these tin-coated fibers by the two-point bending technique rather than t he 5,5 GPa normally found for polymer-coated fibers.