Enhanced Thermo-Mechanical Decoupling Using Fiber Bragg Grating Sensors in Birefringent Fibers for Structural Health Monitoring

Abstract

Fiber optic sensors are increasingly used in aerospace applications due to their lightweight, immunity to electromagnetic interference and ability to measure multiple parameters like strain and temperature. Fiber Bragg Grating (FBG) sensors are particularly promising for Structural Health Monitoring (SHM) but face challenges in distinguishing thermal and mechanical effects, as both induce similar wavelength shifts. Current decoupling methods are classified as extrinsic (requiring additional components) or intrinsic (leveraging sensor properties). While extrinsic methods are effective, they increase system complexity. Intrinsic approaches reduce invasiveness but remain underdeveloped for practical applications. This study introduces birefringent optical fibers with inscribed FBG sensors to address these limitations. Birefringence, caused by refractive index asymmetry, generates two distinct reflection peaks with different sensitivities to strain and temperature, enabling effective decoupling. Experimental validation confirmed the method’s accuracy and repeatability. To enhance performance, an optimized resolution strategy was developed, improving measurement accuracy and reducing errors. Machine learning techniques were also explored to refine data analysis. Results demonstrate that birefringent FBG sensors offer a scalable, non-invasive solution for aerospace SHM. Future research will focus on optimizing sensor integration and performance, with an emphasis on collaboration with industry to enable real-world applications.