Temperature Insensitive and Integrated Differential Pressure Sensor for Liquid Level Sensing Based on an Optical Fiber Fabry–Perot Interferometer

We propose a temperature insensitive optical fiber Fabry–Perot (FP) sensor for liquid level measurement. The sensor is based on a silicon diaphragm and borosilicate glass ferrules. Through the combination of different ferrules, the FP cavity is fabricated without a seal to eliminate the influence of the residual air in the FP cavity, thereby the temperature cross-sensitivity is significantly reduced. The opened FP cavity constitutes a differential pressure sensing structure at the same time. To verify the performance of this sensor, an experiment with an optical fiber pressure and temperature experiment system is carried out. The measuring range is 0.5–1.3 MPa. The sensor has a good monotonic linear response with an accuracy less than 0.4% F.S. (full scale). The measuring error caused by the temperature drift is lower than 0.0007 MPa/K, i.e., 0.09% F.S./K.