The fatigue of high-strength fused silica optical fibers in low humidity

The strength and dynamic fatigue of UV-acrylate coated silica optical fibers were measured as a function of relative humidity in the range ∼0.025–13% at 25 °C. The degradation kinetics of silica in low humidities was investigated and it was found that the reaction order was approximately first-order with respect to humidity. In our previous work, a second-order reaction was found in the humidity range 20–95% RH at 25 °C and the process for obtaining this reaction order was found to be independent of the mathematical form of the kinetic models used. The change in reaction order observed here verifies some earlier results based on the power law which implied a change in the reaction order from ∼2 (15–100% RH) to ∼1 at low humidity (<0.01%).