A Liquid Level Sensor Based on a Race-Track Helical Plastic Optical Fiber

A multi-point liquid level sensor was proposed in this letter, which is based on a plastic optical fiber with a race-track helical structure. The principle of liquid sensing is based on higher modes leak out and regenerate repeatedly in the bend and straight sections, respectively. Therefore, propagation loss was introduced in the bend sections of the fiber submerged under the liquid. The liquid level shift can be detected by observing alterations in the propagation loss changes. The sensor features compactness and independence from the refractive index of the liquid. The level measurement resolution is flexible and expected to reach the same order of magnitude as the diameter.