A review of FBG based sensors with different packaging sensing structures for slope deformation monitoring

Purpose The application effect of fiber Bragg grating (FBG) sensors in slope engineering is highly dependent on the packaging structure design. Reasonable packaging can not only protect FBGs, but also optimize their response characteristics to multiple parameters such as strain, displacement and inclination, improve measurement accuracy and adaptability. The purpose of this paper is to present the latest sensing structure designs and encapsulation methods of information detection of FBG sensors. Research advance and the future work in this field have been described, with the background that displacement and deformation measurements are universal and crucial for slope deformation monitoring. Design/methodology/approach The review systematically analyzes the FBG sensing technology and principle of the sensing elastomer structure design (metal substrate type, tubular type, cantilever beam type, 3D printing type and so on). It critically gives a comparative analysis of their advantages and disadvantages in complexity of structural design, fabrication techniques, range and sensitivity while analyzing various FBG sensors for slope application demonstrating successful studies. Findings FBG sensors primarily use cantilever beam bonding for effective temperature-strain decoupling, though size and installation are drawbacks. Metal bonding/tubular clamping types face temperature/strain transfer issues, whereas 3D printing encapsulation is limited by materials. Slope monitoring employs FBG tilt sensors (measuring inclinometer casing angles) or in situ strain sensors (converting casing strain to displacement), both often using cantilever or 3D printed sensing elements. Ground settlement uses trip/columnar FBG sensors. Mathematical models (especially TIM, CBM) convert inclination/strain to lateral displacement. Research focuses on specific encapsulation advantages (sensitivity, compensation, fabrication) and integrating 3D-printed protective monitoring components. Originality/value The latest FBG sensor configurations for slope deformation monitoring, including metal substrate bonding, tubular clamping, cantilever beam bonding, 3D printing packaging and other structural forms have been proposed and a comparative analysis of their advantages and disadvantages is provided, which can offer valuable insights for future sensor design and application.