Air Gap Fiber Fabry–Pérot Interferometer for Highly Sensitive Micro-Airflow Sensing

This work presents a novel sensor based on an air-gap fiber Fabry-Perot interferometer (AG-FFPI) to identify an extremely low airflow velocity. When a micro airflow flows through the upper side of the sensor, an extremely small pressure difference caused by fluid mechanics makes two fiber endfaces tilt upwards and generates a tiny discrepancy between the two aligned fiber endfaces. This discrepancy of the AG-FFPI changes the air gap, and the center wavelength of the specific interference dips. The proposed sensor can determine the velocity of a micro airflow from a surrounding environment within 0 ~ 1.2 m/s. In addition, the wavelength of shifts in interference fringes is nearly proportional to airflow velocity with a high sensitivity of approximately +33.17 nm/(m · s^-1).