A Comparative Investigation on Performance of Fiber Bragg Grating Soil Pressure Sensors With Different Configurations

Long-term and accurate measurement of soil pressure is crucial for safety monitoring in geotechnical engineering. The diaphragm-type fiber Bragg grating (FBG) soil pressure sensor is currently the most widely used mainstream sensor, but the gratings of this type of sensor are prone to chirping. By adding an additional cantilever beam inside the diaphragm-type FBG soil pressure sensor, a cantilever-type FBG soil pressure sensor with another sensing method is obtained and this type of sensor solves the above problem. This article designed and fabricated an FBG soil pressure sensor with these two sensing methods, and then, the performances of cantilever-type fiber FBG soil pressure sensor and diaphragm-type FBG soil pressure sensor have been investigated. The measuring principle of two types of sensors is introduced, and the diaphragm structure of the sensor is analyzed through the theoretical calculation and finite element analysis (FEA). The performance of the two types of sensors was fully tested through a series of experiments. The experimental results indicate that the sensitivity of diaphragm-type FBG soil pressure sensor is 2363.32 pm/MPa, but the range is only 1 MPa, while the range of cantilever-type FBG soil pressure sensor is 1.8 MPa, but the sensitivity is only 1347.39 pm/MPa. Both types of sensors have good measurement capability, creep resistance, and temperature compensation performance. This article reveals the sensing characteristics of two different configurations of soil pressure sensors, providing valuable design and application references for engineers and technicians.