Devices and methods are presented in which an optical fiber reflectometer and a solar concentrator are used to determine solar reflectivity and absorptivity for opaque and diffuse materials. The measurements can be taken at high temperature, the final aim is to reach 2500 degrees C. Firstly we will present the specific reflectometer and its measurement principles. We will then describe the whole experimental hardware (solar concentrator, associated devices) and the method used to determine solar reflectivity and absorptivity. Finally, we will present examples of results obtained on a metallic sample.