Fiber Sensor for Liquid Level Detection Based on Micro-Arc Air Cavity Structure

A novel liquid level sensor is devised, leveraging the principle of Fabry-Perot interferometry (FPI). The sensor amalgamates micro-arc and air cavity structures. The micro-arc is fabricated through flame pyrolysis, while the air cavity is created by fusion splicing a SiO₂ microtube with single-mode fiber (SMF). When alterations occur in either the liquid level or temperature, the spectral information primarily manifests as variations in reflected light intensity. Consequently, it provides a new perspective for liquid level and temperature measurements. The FPI sensor is a three-wave interference model. To realize low-temperature sensitivity, an optical fiber is fused at the end of FPI to reduce the reflection of the third reflector. The temperature sensitivity of the sensor is measured at 0.0856 dB/°C, the liquid level sensitivity is determined to be 0.2185 dB/mm. Therefore, the sensor is suitable for conducting liquid level measurements in industrial applications. Additionally, the sensor is simple in structure and does not need special treatment, making it highly competitive in industrial production.