Optical Fiber Sensor for PVC Sheet Piles Monitoring

This paper examined the impact of optical fiber sensor design, and its integration to PVC (polyvinyl chloride) sheet piles, on deflection and strain monitoring. Optical fiber sensors based on Brillouin light backscattering (BLS) were prepared, as they can provide accurate strain and deflection measurement results. However, depending on the application of sheet piles systems, high deformation of PVC elements can be observed. Therefore, a fiber sensor design is not trivial. Three types of optical fiber coatings and their integration with PVC sheet piles were investigated. The effect on the value of compressive and tensile strain were analyzed. It has been experimentally proven that PVC sheet piles monitoring, based on BLS method, can be realized using optical fibers with 250 µm, 900 µm, and 3 mm coating diameter. Achieved results are in line with theory. Correction coefficient necessary for 900 µm and 3 mm coatings has been proposed and used to ensure proper strain measurement. It was found that 250 µm coating fiber based sensors can be utilized for PVC strain measurement under low deflection (>1.2 m beam length). On the other hand, sensors based on 3 mm coating fiber, due to a high level of linearity, can be applied to deflection distance measurement under high deformation.