Design of hermetically metal-coated optical fibers to simultaneously minimize thermally and hydrostatic pressure induced stresses

The design of hermetically metal-coated optical fibers to simultaneously minimize the thermally and hydrostatic pressure induced stresses is investigated. The thermally and hydrostatic pressure induced stresses would produce the microbending loss, the delamination of metallic coatings or the static fatigue of the glass fiber, so these stresses should be minimized. The selection of physical properties of metallic coatings and their thicknesses for the minimization of these stresses is proposed. The calculated stresses in hermetically metal-coated optical fibers with some selected metallic coatings are also discussed. It reveals that no pure metal is suitable for the simultaneous minimization of thermally and hydrostatic pressure induced stresses. However, we can expect that the metal alloy with high water-prevention, high tensile strength, low Young’s modulus, low Poisson’s ratio (between 0.2 and 0.25) and low thermal expansion coefficient will be the best metallic materials for the simultaneous minimization of thermally and hydrostatic pressure induced stresses in hermetically metal-coated optical fibers.