Implementation of polymer optical fibre sensor system for monitoring water membrane thickness on pavement surface

Abstract

ABSTRACT Water membrane thickness on the surface of pavements should be monitored constantly and accurately during high-intensity rainfall to evaluate pavement safety. This is critical to the realisation of smart roads. In this study, a water membrane thickness monitoring system is built based on reflective intensity-modulated fibre-optic sensor (RIM-FOS) technology. The system comprises a sensing unit and a weak signal detection circuit, and its monitoring range and accuracy are calibrated by a specific device. Considering the environmental influence, the water membrane thickness–voltage curves at different light intensities and temperatures are obtained. Subsequently, the accuracy and effectiveness of the proposed water membrane thickness–voltage function are validated by comparing them with the outdoor test results. Finally, to ensure the survival rate of the optical fibre and the accuracy of long-term monitoring, a polymer optical fibre (POF) packaged by a process using water-blocking paste and reinforcing steel bars is employed. To prevent the bending loss during embedding from affecting the measurement results, the bending radius is suggested. The results demonstrate that the POF sensor system shows remarkable performance in terms of accuracy and temperature stability. This research will help provide an inexpensive and comprehensive safety assessment method for asphalt pavement.