The Use of an Organosilsesquioxane for the Coating/Cladding of Silica Fibers

The properties necessary for a material to be useful as a fiber cladding (appropriate Δn) and/or coating (provide mechanical protection) were evaluated for an organosilsesquioxane (Owens-Illinois Resin GR 650). The samples were 120 μm silica fibers coated with 12 μm of the cured organosilicon polymer. We observe, from an index profile of the clad fiber, that Δn = 0.04. The tensile strength measured in air (65% RH, 25 °C) was 765 ksi and the dynamic fatigue constant determined under the same ambient conditions was 29, both of which are typical of a mechanically protected fiber. From aging experiments in 90 °C distilled water we observe that the onset for a marked loss of strength with time is ∼1 day for an epoxy-acrylate coated fiber and slightly more than a week for the organosilicon polymer coated fiber, a notable improvement.