The spring constant in the buckling of tightly jacketed double-coated optical fibers

The primary coating in real optical fiber applications is a soft polymer with a low Young’s modulus that is used as a strain buffer to minimize microbending loss. The secondary coating and jacket are hard polymers with higher Young’s moduli and sufficient thicknesses to sustain the mechanical force. The buckling of optical fibers causes additional transmission loss, thereby necessitating that it be minimized. The optical fiber’s spring constant is a critical factor in the buckling phenomenon. Moreover, a higher value of the spring constant corresponds to a higher resistance to buckling. A closed form solution of the spring constant in the buckling of tightly jacketed double-coated optical fibers is presented. The effects of polymeric coatings on the spring constant are also considered. To obtain a higher value of the spring constant and adhere to optical fiber applications, the thickness of the primary coating was decreased, and the Poisson’s ratio of the primary coating and the Young’s moduli and Poisson’s ratios of the secondary coating and jacket were increased. © 1997 American Institute of Physics.