Light transmission of bend insensitive optical fiber

Optical fibers, which can be sharply bent without high transmission losses, are called bend insensitive fibers. These fibers were developed to meet the increased demand of Fiber-To-The-Home (FTTH) applications, to allow for miniaturization of fiber optic sensors and telecom photonic components, etc. Ordinarily the structure and design of these fibers is described and its advantages specified without an explanation of how it functions. In this paper, a model of bent fiber function is proposed. With an improved capability for analysis, accurate calculations and a simplified understanding of bend insensitive fiber function should permit the expansion of fiber applications. The model presented here is based on mode-ray equivalence and applied to multimode bend insensitive fiber with low refractive index trench. A study is made of the influence of directional properties of a light source exciting a waveguide and of the parameters of the fiber on the sensitivity to bending. The dependences of light transmission on the bending radius are derived for various optical fibers and compared with experimental results.