Mechanical Reliability Considerations Of Polymer-Coated Optical Fibers

Abstract

We have investigated effects of polymer coatings on the strength and fatigue properties of silica fibers. In this study, we performed tensile strength, dynamic fatigue, and static fatigue measurements on silica fibers coated with a variety of uv curable polymers. We have identified the coating properties that influence the mechanical reliability of optical fiber. Polymer coatings can provide adequate protection against mechanical abrasion and microbending loss. However, they cannot protect fibers from fatigue because most polymers are highly permeable to water vapor. Among fibers coated with polymers that have different water permeation and adhesion properties, there are considerable variations in fiber strength and fatigue behavior. We observed that both adhesion and water absorption properties of the coating material affect fiber strength and time-to-failure. We showed that the static fatigue parameter can be significantly lower than the dynamic fatigue parameter when the fiber coating has a low water-absorption value. A lifetime estimate of optical fiber based on the dynamic fatigue parameter is unreliable without consideration of the coating properties; and a more reliable estimate should be based on static fatigue testing. The selection of polymer coatings with high adhesion-to-glass and low water absorption values seems to benefit the mechanical reliability of optical fiber. In summary, coating is an integral part of optical fiber in any mechanical reliability consideration of a polymer-coated optical fiber. Adhesion and water permeation properties of a polymer coating will affect the mechanical reliability of optical fiber.