Simple Configuration of a Fiber Optic Sensor for Measuring Deflection in Concrete Beams

This work proposes a simple configuration of a fiber optic sensor (FOS) used to measure deflection in concrete beams. This FOS includes pulleys with a groove to generate a constant drastic loss in the optical fiber (OF). The FOS was characterized as a function of three pulley diameters in a home-made metallic base. The FOS used a multimode (MM) OF since it demonstrated better behavior than a single-mode fiber, and the deflection caused a loss in the OF. This loss was found to be the parameter related to concrete beam deflection. In this way, we carried out characterization to find the best sensitivity. The sensitivity calculated in the laboratory tests using an MM fiber in the proposed FOS with three pulleys of 1.2 cm in diameter was -0.34785 dB/cm. Furthermore, the proposed FOS was validated in a concrete beam in real time using a 50-tons variable load actuator. Finally, the FOS installed in a concrete beam presented a dependency as a function of overload in tons. The sensitivity obtained in the test was -0.02932 dB/cm.