The article describes a numerical method based on Fourier transform for studying propagating optical waves in dielectric planar waveguides. The inverse problem to the known direct one in waveguide investigation is proposed. namely a search of light wavelengths according to taken values of propagation constants. For each constant a set of wavelengths is obtained. https://www.bekindtopets.com/quick-buy-Titans-Pets-First-Reversible-Dog-Bandana-deal-zone/