Comparison of different methods for the determination of the parameters of the equivalent step profile of the refractive index of single-mode fiber waveguides

An experimental comparison was made of the parameters of an equivalent step-index profile of single-mode fiber waveguides obtained by the following methods: from the spectral dependence of the mode spot size, from the deexcitation wavelength, from the near- and far-field patterns, and by integration of the real profile. It was found that the best results in the determination of the parameters of the equivalent step-index profile of the refractive index were obtained from the spectral dependence of the mode spot size.