Influence of drawing conditions on the tensile strength of fluoride glass optical fibers

Abstract

Heavy-metal fluoride glass fibers are currently developed due to their potential ultra-low loss window in the 2 to 4 µm wavelength region, which makes them attractive candidates for future long-distance optical communication links. Extrapolations suggest even lower intrinsic losses for barium fluorozirconate glasses than for silica. However, the tendency of present glass compositions to crystallize makes fiber drawing difficult and results in poor mechanical performance. It is reported here on glass preparation and drawing experiments. Using the standard Zr-Ba-La-AI glass composition the effect of preform surface preparation on fiber tensile strength is demonstrated. Application of a novel ZrOCl2 etching technique, which is described in detail, resulted in improved fiber strength. Drawing temperature has to be controlled in a narrow range of ± 3 K. Under optimized condifions fibers with a mean tensile strength of 400 MPa were obtained, which is an improvement by a factor of 2 in comparison to previous results. Removing preform surface crystals has also a positive effect on fiber attenuation. The etching procedure proved to be a valuable tool in fluoride glass development.