Importance of coatings to optical fiber sensors embedded in 'smart' structures

The importance of coatings to the overall performance of optical fiber sensors embedded in smart host materials is explored with closed-form solutions. Particular attention is paid to the mechanical ramifications of varying the properties and thickness of the coating, when the fiber is embedded in a transversely isotropic host material that is experiencing tensile loading parallel to the optical fiber. Analytical solutions are developed that show that strain concentrations near an embedded optical fiber are highly dependent on the thickness and material properties of the coating. Analytical evidence is presented of the existence of optimum coating material and thickness combinations for a given host material. Depending on the optimizing criterion selected, this optimum choice can minimize or even eliminate stress concentrations either in the host material immediately surrounding the embedded fiber, or in the coating, or in the optical fiber itself.