High-Sensitivity Optical Fiber Temperature-Depth Sensing Array

The study of ocean-related phenomena is inseparable from the temperature and depth of seawater. Fiber optic sensors are essential in marine environmental detection due to low cost, electromagnetic immunity, and easy integration. This paper proposes wha we believe to be a novel temperature-depth sensor based on fiber Bragg gratings (FBG). The sensor achieves high sensitivity using a dual-FBG structure enhanced by etching, polymer packaging, and mechanical design. The temperature sensitivity exceeds 145.16 pm/°C, with a resolution better than 0.007 °C. The pressure sensitivity reaches 48.418 nm/MPa, and the depth resolution is approximately 2 mm. Based on FBGs’ advantage of wavelength division multiplexing, multiple sensor elements form a temperature-depth sensing array. This array enables simultaneous measurement of temperature and depth at multiple points in water environments. The sensing performance of the array is validated through lake experiments. Experimental results indicate that the proposed temperature-depth array has broad application potential in shallow water layers, lakes, wetlands, and other environments.