We show that the refractive-index profile (RIP) of optical waveguides can be determined by analyzing the transmitted near-field pattern with the finite element method. The first step consists in determine the initial guess for the RIP. Then, the selected guess is improved applying a reconstruction procedure with the finite element method. The procedure has been evaluated by comparing the obtained results with experimental measurements obtained by the RNF and <i>m</i>-lines techniques on a pure-silica single-mode fiber and slab waveguide, respectively.