Abstract

Glass fiber lightguides for use in submarine lightwave systems require a 200-ksi (1.4-GPa) proof-test level to survive deep-sea recovery operations. Some military applications require even higher proof-test levels.¹ These demands for high proof-test levels coupled with the use of low-modulus inner coatings to reduce microbending-induced sensitivity have generated interest In the amount of protection offered to the fiber surface by a low-modulus coating.² In general, we have noted a decrease in proof-test strengths from fibers coated with low-modulus primary coatings (as compared with high-modulus coatings) and have attributed this decrease in strength to an increased sensitivity to abrasion by particulate contamination within the coating material. To help quantify this increased sensitivity, a study was undertaken to determine the critical particle size for high proof-test level failures. Alumina particles, in particle size ranges of 1-3, 6-10, 12-15, and 15-20 μm, were added (0.1 wt.%) to high-modulus and low-modulus UV curable acrylate coatings. To achieve such particle size ranges, great care must be taken to avoid tightly bound aggregates. Each particle size range was verified prior to its introduction into the coating material. Lengths of 750 m of fiber from a fire-polished Suprasil SS2F rod were then drawn and coated; 500-m lengths were proof-tested at levels of 50, 70, 100, 150, and 200 ksi. In addition, tensile strength distributions were determined for as-drawn fibers and for fibers previously proof-tested.

© 1985 Optical Society of America