Analysis of Excess Attenuation in Optical Fibers Subjected to Low Temperatures,

Optical fibers which exhibit a dual coating comprised of a low modulus inner layer and a high modulus outer layer at times display excessive attenuation increase at low temperatures. The excess loss may be attributed in part to forces exerted on the optical fiber by the polymer coatings as the temperature decreases, thereby resulting in fiber bending. Fiber bending may occur if the optical fiber assumes a spiral configuration within the low modulus primary coating due to thermal contraction of the secondary coating. Defects in fiber coatings, such as coating eccentricity, fluctuations in coating thickness, and voids between primary and secondary layers, may amplify excess attenuation as the fiber temperature decreases. Author