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Considering measurement accuracies, different models used for the prediction of longterm static fatigue for optical fibres under stress were studied. Optical fibres were wound onto an alumina mandrel with various diameters and immersed in hot water at different temperatures. The determination of model parameters was based on the fit of experimental data to model expressions relating time to failure, applied stress and environmental conditions. It is shown that the differences in allowed stress predictions between models become quite close at short times. The time-to-failure depends on the applied stress applied but also and above all on the ageing temperature and the humidity level. Results from tested fibres indicate a clear strength reduction with increasing temperature or applied stress. [ABSTRACT FROM AUTHOR]

The practical strength of optical fibers was controlled by flaws, usually on the surface. It was well established, furthermore, that such flaws can grow in time so that an initially intact silica optical fiber may undergo delayed fracture from the combined influence of stress levels and the chemical environment as air humidity. On the other hand, glass optical fibers were almost always coated with a polymer immediately after drawing to protect them from subsequent handling damage and from chemical environment. When studying the strength and fatigue properties of the fibers, it was useful to be able to remove this coating in order to directly observe the fatigue properties of the glass in immediate contact with the environment. Silica optical fibers with and without polymer coatings were submitted to bending tests when fibers were aged in air atmosphere and in inert atmosphere. Median fiber strength underlines the role of used atmosphere and that of the polymer coating. [ABSTRACT FROM AUTHOR]