Elastic stability of a dual-coated optical fiber of finite length

Abstract

Dual-coated optical fibers are fabricated at elevated temperatures and operated at low temperature conditions. It is imperative that the fibers remain elastically stable, i.e., do not buckle as a result of the thermal contraction mismatch of the dissimilar materials of the fiber and the secondary coating or, in the case of an optical fiber interconnect, of the fiber and the material of an enclosure, if any. We develop a simple and easy-to-use predictive model that enables one to establish the condition of elastic stability for a dual-coated optical fiber of finite length, and/or to select the coating materials with the most favorable physical properties for such a fiber, and/or to establish the adequate thickness of the primary coating. The fiber is idealized as a free-free beam (i.e., a beam not supported at the ends), and the effect of the embedding medium is mimicked by a continuous elastic foundation. The obtained results can be applied also, with some minor modifications, for the evaluation of the elastic stability of short fibers in fiber-reinforced composites, including nanocomposites.