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

Simultaneously determined results from zero-stress aging and static fatigue measurements in water at 65-degrees, 80-degrees, and 95-degrees-C have been combined into a worst-case fiber lifetime model which shows good agreement between predicted and observed failure times. The model shows that the lifetime in a wet environment of the largest crack at normal service strain (0.1%) is nearly identical to the lifetime of the pristine fiber and that the initial strength and the stress corrosion exponent are of minor importance for the lifetime. In a separate experiment, it is shown that degradation in a water-saturated, jelly-filled cable is significantly slower than when fibers are directly immersed in water. For a fast-degrading fiber, evidence of a strength-increasing mechanism is presented.