DEGRADATION OF STRESSED OPTICAL FIBERS IN WATER - NEW WORST-CASE LIFETIME ESTIMATION MODEL

Simultaneously determined results from zero-stress aging and static fa tigue measurements in water at 65-degrees, 80-degrees, and 95-degrees- C have been combined into a worst-case fiber lifetime model which show s good agreement between predicted and observed failure times. The mod el shows that the lifetime in a wet environment of the largest crack a t normal service strain (0.1%) is nearly identical to the lifetime of the pristine fiber and that the initial strength and the stress corros ion exponent are of minor importance for the lifetime. In a separate e xperiment, it is shown that degradation in a water-saturated, jelly-fi lled cable is significantly slower than when fibers are directly immer sed in water. For a fast-degrading fiber, evidence of a strength-incre asing mechanism is presented.