Formation, growth, and dynamics of the etchant phase on preforms during fabrication of lensed optical fibers

Subject of study. The formation of etchant droplets on the surface of silica optical fiber is studied. Aim of study . The aim of this study is to experimentally determine the effects of etchant droplets formed on the surface of silica fibers in air and within the buffer layer on the characteristics of the optical fiber cladding. Methods . Video of droplet behavior during the etching process was recorded, and Raman spectroscopy was used to determine the chemical composition of the droplets. The dynamics of droplet formation and the surface topographies of the working cones of lensed optical fibers were studied according to the applied etching process parameters. Main results . The results demonstrated the complex nature of droplet formation and motion along the optical fiber during etching based on the buffer-layer thickness and system heating conditions. New data were obtained indicating that etchant droplets have a significant effect on the optical fiber cladding, whether they form in air or within the buffer layer. Spectral analysis of the chemical composition of the etchant droplets was performed, and the final shape of the fiber preforms was described as a function of the process parameters. The results of this study provide data informing the selection of the optimal buffer-layer thickness to produce lensed optical fibers of a specified shape. Practical significance . The practical significance of this study lies in its identification of the optimal conditions for chemically etching optical fibers; implementation of these conditions will accelerate the etching process and help produce higher-quality preforms.