A High-Sensitivity Strain Sensor With Femtosecond Fiber Bragg Grating for Pipeline Deformation Monitoring

Structural health monitoring (SHM) of hydraulic pipelines plays a crucial role in preventing catastrophic failures, particularly when measuring large strains with high sensitivity. This study presents a novel high-sensitivity strain sensor utilizing femtosecond fiber Bragg grating (FS-FBG) technology to overcome the limitations of conventional monitoring techniques in extreme conditions. The sensor incorporates two key components: sensing and measuring members, featuring an innovative skeletonized sensitized shaft design. A pre-stressed FS-FBG is suspended axially within the structure. The relationship between fiber Bragg grating (FBG) wavelength displacement and pipe surface strain was validated using Bernoulli-Euler beam theory and finite element analysis. In order to accurately calibrate the performance of the sensor, a precision pipe deformation device was designed. Experimental results demonstrate that the sensor achieves a sensitivity of 4.19 pm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula>, which is 3.4 times higher than that of the FBG sensor, in the range of 0–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1650~\mu \varepsilon $ </tex-math></inline-formula> of the pipe surface microstrain, and at the same time, it has excellent linearity, creep-resistant performance, and temperature compensation effect. The results provide a reliable solution for large strain monitoring of hydraulic pipelines under severe conditions.