This study integrates metal 3D printing technology, optical fiber metallization, and laser welding preparation – encapsulation processes to design a high-temperature, large-strain optical fiber sensor with low stiffness and a wide measurement range. The aim is to address the challenge of monitoring thermal and mechanical parameters in aeroengine turbine blades. The designed sensor employs a hybrid demodulation method based on fiber Bragg grating (FBG) wavelength and light intensity, enabling precise measurement of temperature and strain. Through theoretical modeling, finite element simulation, and structural optimization of a grooved “8”-shaped spring substrate, the sensor’s reaction force on the measured structure is reduced to 167 N/ε. Experimental results demonstrate that the sensor can achieve a large-range strain measurement of 37520 με, with a temperature linearity of 0.9878 within the range of room temperature to 500 ℃. Additionally, the sensor exhibits excellent temperature-strain decoupling performance, with a maximum decoupling error of less than 8%. These outstanding characteristics indicate that the designed sensor has promising application prospects for high-temperature strain monitoring in aero-engine turbine blades.