Chapter 4 - Optical Fiber Coatings

Abstract

This chapter focuses on the development, science, and performance of protective coatings for optical fiber. Fiber fatigue is an important mechanical property of optical fibers. Pristine silica fibers have the strength of approximately 7 GPa at the ambient condition. However, fibers can experience fatigue when subjected to lower stresses for a long period. Long-term durability of protective coatings is considered to be of considerable importance because fibers installed into outside plant networks are expected to have a minimum service lifetime of 25 years. Low refractive index (RI) coatings are used for cladding of plastic optical fiber or glass cores. They are by nature relatively low-modulus materials and are therefore often protected by overlaying a standard secondary coating. The lower RI coating is preferred for fiber used in laser and amplifier applications. The low RI coating increases the numerical aperture (NA) value, allowing for higher power inputs and thus higher powered lasers. UV-curable coatings designed for the protection of optical fiber have transitioned from single coatings based on epoxy acrylate chemistry to dual-layer coatings based on urethane acrylate chemistry over the past several years.