Strength, crack resistance and optical losses of heat-treated silica fibers coated with non-ferrous metal

Abstract

Metallic coatings currently provide the highest performance for silica fibers. The purpose of the present works predict of crack resistance, in determining the hardness and strength of uncoated and copper-coated optical fibers, as well as in the study of changes in strength parameters and optical losses after thermal effects on the studied optical fibers. The hardness and crack resistance values of silica fibers are measured by indentation. Crack resistance K1c is calculated using a semi-empirical Niihara relationship that relates the indentation size, radial crack length, and crack resistance. It was found that copper coating of silica fibers increases crack resistance 4 times, probably due to the affect of compressive stresses. The tensile strength of the fibers is determined by axial tension and two-point bending methods at a constant loading rate. Using a scanning electron microscopy, the initial crack length is calculated and the size of the characteristic defect is determined.