Determination of the refractive index profile of fiber waveguides by a modified near-field refraction method

A modification of the near-field refraction method was developed for determination of the refractive index profile of fiber waveguides. Side illumination of a fiber and determination of the distribution of the illumination over the fiber end make it possible to eliminate precision alignments and use visual displays. A description is given of the apparatus which can be used to determine the refractive index profiles of multimode and single-mode fiber waveguides both rapidly and easily.