High-Resolution Portable Dual-Point Liquid Level Measurement System Using POF

This paper presents a portable dual-point optical fiber sensor system for continuous liquid level measurement using polymer optical fibers (POFs). The system contains sensor design and integration with smartphone. The sensor design employs a twisted coupling technique, where two bare optical fibers are twisted together, allowing power to transfer from the illumination fiber to the coupled fiber. The 3D-printed casing mounts into smartphone where the sensor system is attached to casing. The light is launched from the smartphone's flashlight and next end of fiber is to the camera. The flashlight serves as the light source, and the camera records intensity variations caused by changes in the liquid level. Experimental results demonstrate a linear response in optical power intensity as liquid levels increase, allowing for precise measurement of levels up to 120 mm simultaneously. Sensor-1 achieved a sensitivity of 0.050%/mm and sensor-2 exhibited a sensitivity of 0.033%/mm, with a resolution of 0.05 mm. Both sensors showed stable and consistent performance during ascent and descent phases of liquid level measurement. This cost-effective, portable sensor system offers high accuracy and reliability, making it suitable for industrial applications such as chemical processing and environmental monitoring.