The main interest of this paper is to design and analyze the performance of an optically activated optical switching between a single-mode optical fiber and a slab waveguide of a photoactive material. A mathematical model is developed for this structure. The paper includes a report on the trials which have been performed in order to fit a switching material in terms of its refractive index, slightly greater than that of the fiber core and provides the required change in the refractive index. A comparison between the predictions of the developed mathematical model and the experimental measurements is introduced. It has been shown that the switching of light between fiber and slab depends on the relationship between the refractive index values of the fiber core and the slab and the geometry of the switch. Design parameters are determined from these results.