Distributed Airflow Sensing Based on High-Spatial-Resolution BOTDA and a Self-Heated High-Attenuation Fiber

An all-fiber distributed airflow sensing method based on a differential pulse-width pair Brillouin optical time domain analysis (DPP-BOTDA) and a self-heated high-attenuation fiber (HAF) is proposed and demonstrated. The HAF heated the sensing fiber, producing a gradient temperature distribution in it through physical contact, where the temperature distribution was obtained by DPP-BOTDA with a spatial resolution of 5 cm. The heat loss caused by the airflow was reflected in the decrease in the Brillouin frequency shift and spatially resolved by DPP-BOTDA. Distributed airflow sensing was experimentally demonstrated for measurements of airflow movement, multiple airflow sources and the deflection angle of the airflow. The positioning error of the airflow was no larger than ~2.2 cm; for the deflection angle measurements of the airflow, the maximum demodulation error was 2.5° within the angle range of 0–30°.