ELASTIC STABILITY, FREE-VIBRATIONS, AND BENDING OF OPTICAL-GLASS FIBERS - EFFECT OF THE NONLINEAR STRESS-STRAIN RELATIONSHIP

We evaluate the effect of the nonlinear stress-strain relationship on elastic stability, free vibrations, and bending of optical glass fibers. The analysis is carried out under an assumption that this relationship, obtained for the case of uniaxial tension is also valid in the case of compression, and is applicable to bending deformations as well. We examine low-temperature microbending of infinitely long dual-coated fibers, elastic stability of short bare fibers, free vibrations of long fused portions of light-wave couplers that are subjected to uniaxial tension, and bending deformations of optical fibers that experience large deflections. We conclude that the nonlinear stress-strain relationship in silica materials can have a significant effect on the mechanical behavior of optical fibers and that, since the experimental data were obtained for tensile strains not exceeding 5%, future experimental research should include evaluation of the nonlinear stress-strain relationship, both in tension and compression, for higher strains and for high-strength fibers (such as, for instance, fibers protected by metallic coatings).