The Effect Of Fiber Coating On The Radiation Response Of Fluorosilicate Clad, Pure Silica Core Step Index Fibers

The effect of various coating materials on the total dose radiation sensitivity of 100/140 micron fluorosilicate clad, pure fused silica core step index fibers has been investigated. Various combinations of coatings allowed us to study the effects of coating type, coating thickness, single versus double dipped coatings, coating weight and coating cure intensity and duration. We find that the response of the fiber to Co-60 irradiation to 100 krads(Si) is influenced by the characteristics of the first coating deposited on the fiber, but is not sensitive to the second coating deposition. The most radiation resistant fiber was that coated with a polyimide, which is cured at a high temperature, while the least resistant was an acrylate coating cured by exposure to ultraviolet light. This result is fortuitous for space applications since the polyimide coating is also a low-outgassing, wide-temperature range coating material. We suggest that the variation in radiation response may be due to a post-drawing anneal occurring during coating cure which minimizes drawing-induced defects.