This paper presents an experience in designing, manufacturing and testing the Fresnel lenses (FLs) for sunlight concentration in photovoltaic modules with multi-junction solar cells (SCs). A power ray tracing model is used for calculating and optimizing refractive profile parameters and obtaining optical-power characteristics (OPCs) of Fresnel lenses. In searching the optimum combination of the lens aperture, its focal distance and profile configuration, the optimization criterion was the maximum of the average sunlight concentration at high optical efficiency in the focal spot of minimum size. Analysis of characteristics of circular Fresnel lenses with conical (the facet generating lines are straight ones) and curvilinear (the facet generating lines are curved ones) refracting surfaces has been carried out. The effect material parameters on the lens optical efficiency were studied. Molds for Fresnel lens formation and experimental specimens were fabricated and a control of their profile parameters has been done. A degree of the effect of the light flux characteristics and Fresnel lens geometrical imperfections on validity of the experimental data interpretation has been examined. The correction procedure have been applied in the calculation model to establish the lens optical efficiency values at standard irradiance conditions.