Cascaded microfiber interferometer-fiber Bragg grating sensor for decoupled strain and temperature measurement

An optical fiber sensing scheme for decoupled strain and temperature measurement is investigated based on a cascaded microfiber interferometer-fiber Bragg grating (MFI-FBG) configuration. MFI functions as the primary strain-sensitive element owing to its strong evanescent-field interaction, while FBG is designed to operate as an independent temperature reference. Experimental results indicate that the MFI exhibits a linear wavelength response to applied strain, with a sensitivity of 0.0226 nm/µɛ and a linearity coefficient (R²) of 0.9875. Temperature characterization experiments further demonstrate that both sensing units maintain stable and repeatable responses, with sensitivities of 0.0112 nm/°C for the MFI and 0.0075 nm/°C for FBG, respectively. By exploiting the distinct response characteristics of the two sensing components, a sensitivity matrix is established to effectively suppress strain-temperature cross-sensitivity, enabling accurate and independent demodulation.