The paper presents the results of works on a planar optical amplitude refractometer. On the basis of ion exchange Ag+ - Na+ in glass, channel lightguide sensors are produced. Further on, they will be masked by an appropriate dielectric layer except for a window, where the sample interacts with the waveguide. A planar structure prepared in this way constitutes the basic element of the planar refractometer. Technological and geometric parameters of structures produced influence refractometer transmission characteristics. In the range of lower values of refractive indexes, sensitivity of the refractometer can be increased if the channel waveguide has the shape of a slowly changing sinusoid.