Lifetime of Pristine Optical Fibers

摘要

The strength and lifetime of pristine optical fibers were studied. A model for the crack nucleation on a flat surface is proposed. Due to the external stress and a stress-corrosion reaction, a stable surface deformation develops into a crack during the strength and lifetime experiment. The activation volume determines the stress dependence. This model is applied to the lifetime description of pristine optical fibers. An analytical expression for the fatigue parameter shows that it depends on the local stress. The effect of water and other compounds in an aqueous environment on the lifetime is studied. At high pH the corrosion reaction is faster. In ammonia and amine solutions the lifetime is much shorter than in water. Ammonia diffuses relatively rapidly through the coating layer; for a phosphate solution the coating is impermeable. The presence of small amounts of amines and phosphates in the coating material has a large influence on the fiber lifetime obtained. The fiber coating determines to a large extent the chemical environment during the lifetime.