The presence of thin cover layer on planar waveguide influences its propagation characteristics. A generalized m-line
spectroscopy method enables the evaluation of the parameters (the refractive index, n and the thickness, t) of the subguiding
layers deposited on a planar waveguide. In this paper algorithm for determination of the parameters of the thin
layer (deposited on waveguide with previously evaluated index profile by m-line method) has been presented.