Christopher A. Schantz

Properties of silicon oxynitride coated fatigue-resistant fibers

Optical fibers coated with a thin silicon oxynitride film have shown a dramatic reduction in static fatigue susceptibility compared with fibers lacking such a coating.1,2 However, their fast fracture strength is ≤3.1 GPa rather than the 5.0 GPa typical of conventional fibers. This strength reduction could become a problem if required proof test levels exceed 2.0 GPa. Possible causes for this reduced strength include abrasion of the underlying fiber by the film during deposition or a stress concentration at the surface of the fiber due to rupture of the film under stress. Film rupture is expected If the total tensile stress In the film, including Internal stresses, exceeded its (unknown) tensile strength.