Real-time Pressure Measurement Method based on Rapid Phase Demodulation of Multi-cavities F-P Sensor

In this paper, a novel method for real-time pressure measurement based on rapid phase demodulation of multi-cavities Fabry-Perot (F-P) sensor is proposed. In the demodulation system, according to the principle of low-coherence interference, birefringent crystals, polarizers and analyzers are used to obtain orthogonal signals, which can significantly reduce the influence of irrelevant F-P cavities on the demodulation result, indicating that the method is suitable for rapid demodulation of F-P sensors containing multiple cavities. Experimental results also confirm that the method is able to demodulate the signal of F-P MEMS sensor in real-time. By using the four-quadrant inverse tangent operation instead of differential cross multiplier algorithm to calculate the phase of the F-P sensor, pressure in the range of 110 kPa -200 kPa is measured in real-time, with the demodulation rate of 5 kHz. The measurement errors are less than 0.41 kPa, and the standard deviations are less than 0.25 kPa. The proposed method provides a new idea for the rapid demodulation of F-P sensors containing multiple cavities, and has great potential in promotion and applications of real-time pressure measurement, such as dynamic pressure of aero-engines, shock waves and so on.