Strain and temperature cross-sensitivity decoupling method via a single glass fiber-reinforced polymer encapsulated chirped fiber Bragg grating

Abstract

Distinguishing the temperature and strain in fiber Bragg grating (FBG) sensing remains a critical challenge because of the inherent cross-sensitivity, as conventional multi-grating configurations are susceptible to temperature-induced errors arising from spatial thermal heterogeneity. Herein, we propose what we believe to be a novel single chirped fiber Bragg grating (CFBG) sensor encapsulated in a glass fiber-reinforced polymer (GFRP) for simultaneous dual-parameter detection. The GFRP encapsulation design simultaneously enhances strain transfer efficiency and ensures thermal stability, while the sensing mechanism exploits the distinct differential spectral responses of the central wavelength (-0.98 pm/με, 36.49 pm/°C) and bandwidth (-0.065 pm/με, 3.77 pm/°C) to achieve intrinsic thermal synchronization. The theoretical and experimental results demonstrated excellent linear relationships, with correlation coefficients exceeding 0.99 between the spectral parameters and applied stimuli. Crucially, thermal expansion compensation in GFRP encapsulation results in wavelength drift suppression with an average relative error of <1.2%, halving the sensor count compared to traditional array-based systems. This approach offers a potential solution to the long-standing precision-complexity trade-off, providing a practically viable solution for aerospace composite monitoring requiring stringent parameter synchronization.