The use of sensors and optical fibers for monitoring structures is continuously growing. Strains, displacements, accelerations, temperatures are just a few of the monitoring possibilities. In the case of dam structures, concrete face rockfill dams constitute a type of structures where the monitoring of water infiltrations is of particular interest. In large structures of this type, opening of slab joints is a common effect of general strain distributions, but crack formation may also occur as a result of high compressive stresses, during and after the reservoir filling stage. In this context, this paper verifies, experimentally, the applicability and the response of a distributed fiber optic monitoring system in the identification of infiltration spots and its potential sizes. The experimental tests confirm the technical feasibility of detecting infiltrations, but did not show clear evidence of their sizes.