Environmental effects on fatigue and lifetime predictions for silica optical fibers

This paper reviews the dependence of strength and fatigue of fused silica optical fiber on the environmental parameters temperature, humidity and pH. It is shown that the stress corrosion parameter, n, is not a constant but depends on the nature of the environment. Further, different kinetic forms for the stress corrosion kinetics lead to different interpretations of experimental results. Since lifetime predictions are very sensitive to the value of n and the kinetic form, it is important to know which form is correct. It is shown that the empirical power law form that is almost exclusively used by the fiber optics industry provides a good fit to fatigue data for high strength fiber, but an exponential form provides a more self-consistent description of fatigue in different environments.