Detection and monitoring of multiple cracks using distributed fiber optic sensor

Development and propagation of cracks have a greater probability to deteriorate the integrity of a mechanical structure. Hence it is required to detect and monitor the cracks in order to prevent potential failure. In this paper we have proposed a fully distributed crack sensing system based on OTDR. We have used a novel `S'-type fiber layout to increase the sensitivity while preserving the distributed nature of the sensing system. Experiments have been performed to localize the crack positions and investigate the power losses due to crack openings on acrylic sheets. The results show an increase in sensitivity by ~ 1.43dBm/mm of crack opening with the proposed `S'-type fiber layout.