Hydrostatic pressure and thermal loading induced optical effects in double-coated optical fibers

Abstract

The stresses, microbending losses, and refractive index changes induced simultaneously by hydrostatic pressure and thermal loading in double-coated optical fibers are analyzed. The lateral pressure and normal stresses in the optical fiber, primary coating, and secondary coating are derived. Also presented are the microbending losses and refractive-index changes in the glass fiber. The normal stresses are affected by the hydrostatic pressure, temperature drop, material properties of the primary and secondary coatings, and their thickness. To minimize the microbending losses, the polymeric coatings should be suitably selected, and it is found that the thickness, Young’s modulus, and Poisson’s ratio of the secondary coating should be increased, but the Young’s modulus and Poisson’s ratio of the primary coating should be decreased. Similarly, in order to reduce the changes of refractive index in the glass fiber, the thickness, Young’s modulus, and Poisson’s ratio of the secondary coating should be increased, and on the contrary the Young’s modulus and Poisson’s ratio of the primary coating should be decreased.