This chapter presents the application of fiber optic sensor technology in the monitoring of a load test. First, the description of the fiber optic technology is described with main emphasis in the case of distributed optical fiber sensors (DOFS), which have the potential of measuring strain and temperature along the fiber with different length and accuracy ranges. After that, two laboratory tests in reinforced and prestressed concrete specimens show the feasibility of using this technique for the detection, localization, and quantification of bending and shear cracking. Finally, the technique is applied to two real prestressed concrete bridges: in the first case, during the execution of a diagnostic load test; and in the second case, for the continuous time and space monitoring of a bridge subjected to a rehabilitation work. These experiences show the potential of this advanced monitoring technique when deployed in a load test.