Fabrication of Oxide Glass Coated Fluoride Glass Optical Fibers for Durability and Strength Improvement
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FABRICATION OF OXIDE GLASS COATED FLUORIDE GLASS OPTICAL FIBERS FOR DURABILITY AND STRENGTH IMPROVEMENT
YASUTAKE OHISII, KAZUO FUJIURA AND SHIRO TAKAHASHI NTT Opto-Electronics Laboratories, Tokai-Mura, Ibaraki-Ken, JAPAN
319-11
ABSTRACT
The crystallization of fluoride glass being in contact with oxide glass is investigated using thermal analyses to perform oxide glass coating for durability and strength improvement. The chemical reaction does not occur in the fiber drawing temperature range and begin at the melting temperature of fluoride glasses. The crystallization of fluoride glass is suppressed by contact with oxide glass. Smooth contact between fluoride and oxide glasses is confirmed.
INTRODUCTION Fluoride glass optical fiber is one of the promising candidates of low loss mid-infrared optical transmission media. However, those mechanical properties are serious problems in the practical use, because their poor durability to humidity makes their mechanical properties sensitive to environmental atmosphere. The intrinsic mechanical strength of fluoride glass optical fibers has been estimated as 2 GPa[1]. Though some efforts have been made to improve the mechanical properties, high mechanical strength has not yet been attained[2],[3]. Polymers, such as UV-curable acrylate and TEFLON-FEP, have been used as coating materials for fluoride glass optical fibers. However, as those materials have high permeability of water, they are not adequate for fabrication of high strength fluoride glass optical fibers. Hermetic coating for fluoride glass optical fibers has been tried using Si0 2 , TiN, BN and so on [4]. The application of hermetic coating has not been performed in drawing process of fluoride glass optical fibers. Oxide glasses have high chemical durability compared with fluoride glasses in general and their permeability of water is much lower than polymers. The coating of oxide glasses on fluoride glass optical fibers is thought to be a promising procedure to improve their mechanical properties. However, it has been considered that the Mat. Res. Soc. Symp. Proc. Vol. 172. ©1990 Materials Research Society
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crystallization at the interface between fluoride and oxide glasses is a serious problem. Though there are some attempts for the oxide glass coating, high strength fibers have not yet been fabricated[5],[6]. In this study, the effect of oxide glass being in contact with fluoride glass on the tendency of crystallization of fluoride glass has been investigated in order to fabricate high strength fluoride glass optical fibers.
EXPERIMENTAL
Lead oxide-based glass, whose system is PbO-B 2 0 3 -Bi 2O 3 -TeO 2, was used as a coating material. Thermal analyses, such as DTA-TGA, DSC and TDA, were made for lead oxide-based glasses, ZBLYAL and ZBGA, in the Ar-atmosphere. Especially, DTA-TGA and DSC measurements were performed for powdered mixtures of a lead oxide-based glass and the fluoride glasses. The Young's modulus for the lead oxide-based glass was obtained using a supersonic measurement method. Oxide glass
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