Monofiber-based temperature and strain discrimination using heterogeneous waveguide Bragg gratings

The identical responses of fiber Bragg grating (FBG) sensors to temperature and strain limit their practical applications.To address this challenge, we propose and demonstrate a monofiber sensor capable of discriminating between temperature and strain by leveraging the distinct thermo-optic properties of two heterogeneous waveguides.Specifically, a pair of waveguide Bragg gratings was inscribed in different sections of a panda polarisation-maintaining fiber (PMF) using spherical-aberration-assisted femtosecond (fs) laser fabrication.When subjected to temperature changes, the two Bragg resonance peaks exhibited distinct responses, whereas their strain responses remained consistent.Consequently, the monofiber sensor achieves discrimination without requiring additional isolated compensation.The proposed sensor demonstrates an order-of-magnitude improvement in strain measurement accuracy compared to conventional isolated temperature-compensation methods under dynamic temperature changes.