Cryogen adaptive and integrated differential pressure sensor for level sensing based on an optical Fabry–Perot interferometer

In this paper, we introduce a cryogen-adaptive sensor based on a micro-electromechanical system (MEMS) for level measurement of cryogenic fluids. The sensor is fabricated by an optical fiber inserted in a glass ferrule and an integrated Fabry–Perot (FP) chip using the MEMS technique. We carried a liquid nitrogen level measurement experiment to verify the performance of the sensor and a low coherent interference system is used to transform the liquid level to absolute phase. The measuring range is 24 cm and can be expanded more widely. The experimental results show that the sensor has a good monotonic linear response (coefficient determination R 2 > 0.998 ), and the measurement error is less than ± 5 m m in liquid nitrogen. The excellent cryogenic temperature performance from − 260 ∘ C to − 100 ∘ C also is demonstrated, which shows the potential application in level measurement of various cryogenic liquids.