“…Universal numerical methods of reconstruction of refractive index of dielectric objects are designed for coefficient inverse diffraction problems and ignore the waveguide properties of the devices (see, for example, [4]). The methods for the determination of the optical characteristics of dielectric waveguides are proposed for waveguides of some special forms (see, for example, [16,18]). For instance, the waveguide spectroscopy is widely used for planar (one-dimensional) multi-layered waveguides [11].…”