Measurement of refractive-index profile of single-mode optical fibers by the propagation-mode near-field method

The refractive-index profiles of single-mode optical fibers are measured by the propagation-mode near-field method. The near-field pattern of a propagation mode is measured with a vidicon camera and a microscope to magnify the pattern. The presented system is very suitable for automatical and quick measurement of the refractive-index profile of single-mode fibers.