Continuous liquid level sensor based on a reflective long period fiber grating interferometer

A continuous liquid level sensor (LLS) based on an in-fiber Michelson interferometer is proposed and experimentally demonstrated. The in-fiber Michelson interferometer is formed by a single long period grating (LPG) together with a reflective mirror at the end of the fiber. The portion between the mirror and LPG is immersed in the liquid to be measured as an LLS sensing probe, and the liquid level can be measured by monitoring the wavelength of interference fringes of the in-fiber Michelson interferometer. The experimental results show that the proposed LLS has a good sensing linearity and sensitivity.