Hybrid Glass Coatings for Optical Fibers. Preliminary Results of Coating Performance on Silica Fibers

摘要

Key requirements for specialty optical fibers engaged in various aerospace applications are extended lifetime and superb performance combined with small fiber diameter, minimal bend radius and ease of terminations. To address these requirements, the use of novel inorganic -organic materials called hybrid glass was proposed as single and double coats. Several types of hybrid glass candidate materials were applied on line on silica fibers as 7-35 μm thick single- or double -layer coats. The hybrid glass applied on silica fibers formed a non-strippable glasslike layer that was permanently bonded to the fiber surface. SEM analysis showed smooth, crack-free surfaces of the coatings and their strong adherence to the glass surface. To evaluate the protective ability of the hybrid coatings, the 2-point bending testing (dynamic fatigue) was controlled in a controlled temperature and humidity environment. Dynamic fatigue plots, the stress corrosion parameter n, Weibull strength distribution plots and average bending strength were calculated from the 2-point bending test data for each type of coated fiber tested. Two polymer coated fibers were used as reference and were tested as well. The hybrid glass coatings offered higher values for both fiber strength and n than those found for reference fibers. The UV induced photopolymerization of coating materials crosslinked the inorganic- network. The UV curing contributed also to the condensation process of inorganic constituents of the coatings and their permanent bonding to the silica fiber surface.