Analysis of Long-Term Optical Effects in Double-Coated Optical Fibers Induced by Hydrostatic Pressure and Thermal Loading

The hydrostatic pressure and thermal loading simultaneously induced optical effects in double-coated optical fibers in the long-term are analyzed by the viscoelastic theory. Using the Laplace transformation method, close-form solutions for the microbending loss and refractive index changes are obtained. The results of the microbending loss are initially identical to those obtained by the elastic analysis, and then decrease gradually as time progresses. The microbending loss and refractive index changes of the glass fiber are functions of the material properties of the primary and secondary coatings. To minimize the microbending loss and refractive index changes in the long-term, the Young's modulus of the primary coating, and the viscosity and Poisson's ratio of the secondary coating should be increased. Nevertheless, the viscosity and Poisson's ratio of the primary coating, and the Young's modulus of the secondary coating should be decreased.