Viscoelastic analysis of optical effects in double-coated optical fibers induced by axial strain and hydrostatic pressure

The axial strain and hydrostatic pressure simultaneously induced optical effects in double-coated optical fibers are analyzed by the viscoelastic theory. Using the Laplace transform method, the linear viscoelastic–linear elastic correspondence principle, and the compatibility conditions of displacement at interfaces, close-form solutions for the microbending loss and refractive index changes are obtained. The results can be reduced to those obtained according to elastic analysis. To minimize the microbending loss, the polymeric coatings should be suitably selected, and it is found that the Youngʹs modulus, Poissonʹs ratio, and viscosity of the primary coating should be decreased. Nevertheless, the Youngʹs modulus, Poissonʹs ratio, and viscosity of the secondary coating should be increased. Similarly, to minimize the refractive index change, the same criteria should be applied to the choice of the secondary coating material.