Determination and calculation of chromatic dispersion in two-layer single-mode fiber waveguides

A comparison of the measured and calculated chromatic dispersion was made using a rigorous electrodynamic formulation of the problem of a single-mode fiber waveguide and the model of an equivalent step refractive index profile. An analysis is made of various methods of constructing the equivalent step profile from the refractive index profile of a blank of a waveguide and the spectral dependence of the size of the mode spot. It is shown that the parameter of the equivalent step profile is best obtained from the higher-order moments of the refractive index profile. It is suggested that the radius of the core of a single-mode fiber waveguide be determined from the condition of equality of the experimental and calculated cutoff wavelengths of the first higher-order mode.