UV-curable formulations for UV-transparent optical fiber coatings I. Acrylic resins

A UV-curable optical fiber coating transparent in the deep UV has been developed to allow a Bragg grating to be directly engraved on the fiber by laser exposure through the coating. Polydimethylsiloxane-acrylate resins were found to give the best performance with respect to the monomer reactivity and the UV-transparency of the polymer coating. Among the various radical photoinitiators tested, an acyl-phosphine oxide proved to be the best suited because of its high reactivity, fast photolysis, and lack of absorbing photoproducts at the writing wavelength, under the selected curing conditions. A 60 mum thick optical fiber coating having more than 50% transmission at 248 nm has been obtained. This optical fiber coating exhibits an excellent photochemical resistance upon exposure to an intense UV laser beam, thus making it suitable for engraving of a fiber grating through the polymer coating. (C) 2003 Elsevier B.V. All rights reserved.