Journal of Northeastern University(Natural Science) ›› 2022, Vol. 43 ›› Issue (11): 1529-1535.DOI: 10.12068/j.issn.1005-3026.2022.11.002

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A Demodulation Algorithm for Fiber-Optic F-P Sensor Based on Fast Fourier Transform and Cosine Similarity

FU Ya-ping1,2, WEN Da1,2, WANG Qiao-yun1,2   

  1. 1. School of Information Science & Engineering, Northeastern University, Shenyang 110819, China; 2. Hebei Key Laboratory of Micro-Nano Precision Optical Sensing and Measurement Technology, Qinhuangdao 066004, China.
  • Published:2022-12-06
  • Contact: FU Ya-ping
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Abstract: Aiming at the demodulation of the Fabry-Perot(F-P)sensor, a cavity length demodulation algorithm based on fast Fourier transform and cosine similarity(FFT-COSS)is proposed. Firstly, the fast Fourier transform is used to determine the rough measurement value of the cavity length, and then the exact cavity length value is obtained in combination with the cosine similarity algorithm as the final demodulation result of the F-P cavity. Simulation results show that the FFT-COSS algorithm controls the demodulation error to ±0.2nm and the average time of a single demodulation to 1s. The algorithm is applied to a thin-diaphragm F-P sensor micro-pressure test system made of a mixed graphene diaphragm and polymethyl methacrylate(PMMA). Experimental results show that the fitted R-squared of the FFT-COSS algorithm reaches 0.9908 and the cavity length resolution is better than 0.6218nm.The average time of a single demodulation is controlled at 1s, which agrees with the simulation results.

Key words: fiber-optic F-P sensor; thin film sensor; fast Fourier transform; cosine similarity; cavity length demodulation

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