Temperature dependence of the transition in static fatigue of fused silica optical fiber.

Static fatigue (log t = -nlog sigma + log K) of fused silica fiber shows a transition in slope (n) which departs significantly from the usually assumed linear dependence. This characteristic is determined for bare fiber in water from 30-90C over the pH range 1-14. The expression for static fatigue is expanded to include terms for temperature and pH, however the expression is emperical and not founded on a physical model. Thus the reliability of extrapolations cannot be assured. Even so, a modest extrapolation of these results together with an exemplary design curve for prooftested fiber, indicates that for conservative service life predictions, the existence of the transition at long term should be considered a reality.