Assessment of soil-embedded tapered POF sensor for geotechnical monitoring

Plastic optical fiber (POF) sensors for geotechnical monitoring have gained popularity due to their advantages over traditional methods like inclinometers, strain gauges, and settlement plates, which face issues with installation, accuracy, and long-term efficacy. POF sensors offer distributed sensing, enhanced sensitivity, electromagnetic interference tolerance, and durability under adverse conditions. However, embedding POF sensors in soil presents challenges such as uneven distribution, variable sensing performance due to soil structure and installation methods, and complicated calibration processes. Factors like soil temperature, moisture, and chemical interactions, as well as biological activity, abrasion, and physical disturbances, can affect sensor durability and effectiveness. Research shows that applying pressure to the fiber optic sensor at varied soil depths increases sensitivity. Signal loss increases with tapering length and core diameter, enhancing sensitivity. In sandy soils, sample 'D' (4 cm tapering length, 0.98 mm core diameter) performs best, while samples 'l' and 'F' excel in peat soils and coarse sandy soils, respectively. Further research and development are necessary to improve the reliability and flexibility of POF sensors for geotechnical monitoring, addressing current limitations in sensor distribution, calibration, and long-term performance.