The Effects Of Ionizing Radiation On Various Core/Clad Ratio Step Index Pure Silica Fibers

Under past radiation test results, it was observed that various combinations of coatings changed the radiation response characteristics of pure fused silica core step index fibers. The most radiation resistant fiber was that coated with a polyimide, which is cured with a high temperature. Based on this fact, additional testing was performed on polyimide coated fibers fabricated from different preform core/clad ratios. Our preliminary results indicated that the smaller the core/clad ratio the better the performance of the radiation response of the fiber. These results are fortuitous for space applications, since the polyimide coating is also a low-outgassing, wide-temperature range, small size fiber coating material. The test results indicate that the variations in radiation response may be due to a post-drawing anneal occurring during coating cure which minimizes drawing-induced defects.