Study On The FBG Dynamic Demodulation Technology Based On The BBWE-FBG Demodulation Algorithm

As a high-quality sensing element,Fiber Bragg Grating(FBG)has been widely used in various fields of industrial engineering with its characteristics of high temperature resistance,high corrosion resistance and electromagnetic interference resistance.FBG demodulation technology has always been the focus of research in the FBG sensing technology system,especially the dynamic demodulation technology is needed by practical problems.Based on this practical need,this paper has carried out related research on the dynamic demodulation technology of FBG.By summarizing the research status of FBG sensor and its demodulation technology,as well as the temperature and strain sensing mechanism of FBG,the demodulation schemes and demodulation algorithms in common use are compared and analyzed.An improved Buneman-Bragg Wavelength Estimation(BBWE)-FBG demodulation algorithm based on Buneman frequency Estimation is introduced in detail,and its advantages in computational cost,anti-interference and demodulation resolution are expounded.And relying on the tunable laser demodulation method and spectral detection method,the experimental verification was carried out.The main work of the paper is as follows:(1)A set of FBG demodulation system with Distributed Feedback Laser(DFB)sweeping as the core is built.The overall system consists of DFB Laser,driving circuit module,temperature control module,circulator,data acquisition module,photoelectric conversion module and other modules.The BBWE-FBG demodulation algorithm is selected.A temperature control experiment system is built to conduct static temperature experiment on the demodulation scheme,and the experimental results prove the feasibility of the scheme.(2)The Bay Spec spectral demodulation module and broadband light source were used to build the hardware system.The demodulation algorithm was BBWE-FBG demodulation algorithm and compared with Gaussian fitting algorithm.Under the condition that the spectral acquisition rate was 2k Hz and the minimum optical frequency interval of the sampling spectrum was 0.156 nm,the demodulation resolution could reach 0.028 pm.It is obviously better than the 0.27 pm resolution of Gaussian fitting,which proves the advantages of demodulation resolution and anti-noise performance.The paper further explores the demodulation resolution of the algorithm at different spectral acquisition rates.The experimental results show that the control temperature is 20℃,the spectral acquisition rates are 2.5k Hz,5k Hz,7.5k Hz,and the minimum optical frequency interval of the sampling spectrum is 0.156 nm.The demodulation resolution of the system can reach 0.032 pm,0.154 pm and 0.24 pm respectively.(3)The performance of the dynamic demodulation system is experimentally tested based on the cantilever beam experimental device.The results show that: when the natural frequency of the cantilever beam is 85 Hz,the central wavelength change curve and the amplitude-frequency characteristic curve obtained from the dynamic demodulation at different frequencies are stable by providing external dynamic signals through the vibration experimental platform.The method proposed in this paper provides a new algorithm exploration for dynamic demodulation of FBG,and it is hoped that higher dynamic demodulation resolution can be obtained.