Humidity dependence of the fatigue of high-strength fused silica optical fibers

Strength and dynamic fatigue behavior of silica fibers has been measured as a function of ambient humidity. Bare and polymer-coated fibers were compar ed to determine the influence of the coating, The results verify earlier wo rk that suggests the degradation reaction is approximately second order wit h respect to humidity. However, we verify this result using rigorous data a nalysis techniques and, unlike the earlier work, the result is shown to be independent of the form of the kinetic model for crack growth. Trends in th e calculated fatigue parameters illustrate that a simple exponential crack growth law best describes the humidity data. No significant differences wer e found between coated and bare fibers, provided the coated fibers were pro perly equilibrated. A data analysis methodology is given for obtaining vali d reaction orders independently of the crack growth law form.