Research On Remote Fabry - Perot Pressure Sensing System And Demodulation Algorithm Based On Polarization Low Coherence

Optical Fabry-Perot pressure sensor has broad application prospects in deep sea pressure monitor,high temperature oil and gas development,biomedical sensing and other fields due to the advantages of anti-electromagnetic interference,corrosion resistance,low attenuation and so on.Optical Fabry-Perot pressure sensor combined with low coherence demodulation technology has high demodulation accuracy,wide measuring range and can be used for long distance pressure sensing.In order to meet the demands of long-distance and high-precision pressure sensing,this paper studied the structure of single-mode fiber optic Fabry-Perot pressure sensor and proposed a pressure sensor with a silicon ring structure.After studying the characteristics of low coherence interferogram in single-mode sensor system,we proposed an improved phase-based method by using a filtering window on the low-coherence interferogram.The specific research contents of this paper include:1?The multi-beam interference model and optical signal coupling model of FabryPerot pressure sensor based on single-mode fiber are studied.After simulation,the best parameters of two structures of single-mode sensors based on glass substrate structure and silicon ring structure are respectively solved firstly.Then the low coherence interference sensing principle and the demodulation principle of the polarization low coherence interferometer are introduced.Finally,the fabrication process of vacuum sealed sensor based on MEMS technology and the packaging technology of singlemode sensor with silicon ring structure are introduced.2? We have constructed a polarization-low-coherence single-mode fiber demodulation system.After analyzing the characteristic of the interference image in a single-mode system,we proposed an improved demodulation method by adding a filtering window on overlapping interference fringes.Through theoretical derivation and numerical simulation,we proved the correction of our proposed method that the fringes phase can be demodulated nondestructively after applying a symmetrical filtering window nearby the envelope peak.The effects of window shape,window size and different signal-to-noise ratio on demodulation results are also studied.3?A low-coherence interferometric demodulation system based on single-mode fiber was constructed.Firstly,the nano-displacement stage was used as a standard source to demodulate the Fabry-Perot cavity length to verify the effectiveness of the windowing algorithm.In order to analyze the performance of two structures of sensor above mentioned,experiments with SMF Fabry-Perot(F-P)air pressure sensing system were carried out.The experiment results showed that the linear fitting error of singlemode sensor based on silicon ring structure combined with our method decreased to less than 0.53‰ in full 283 kPa scale and the transmission distance extended to 20 km,which is apparently superior to conventional phase-based method.