Research On Optical Fiber F-P Integrated Detection System For Temperature And Pressure

In the field of biomedicine,real-time and accurate monitoring of the physiological parameters of the human body can provide accurate quantitative indicators for clinicians to judge the condition,surgical treatment and postoperative care.Although traditional electrical sensors can monitor physiological parameters in vivo,they are easily affected by electromagnetic interference,and the stability and accuracy of measurement cannot be guaranteed.Optical fiber sensing technology has the advantages of anti-electromagnetic interference,small size and good biocompatibility,and provides an effective method for in vivo monitoring.In response to this,this paper proposes a temperature and pressure integrated sensing probe and system based on an optical fiber Fabry-Perot(F-P)interferometer.The main research contents are as follows:(1)In view of the technical limitations of existing temperature and pressure composite sensors and fiber-optic F-P sensors,the sensing mechanism of a temperature-pressure integrated probe based on a cascaded double F-P cavity structure is studied.The interference spectral characteristics of the cascaded double F-P cavity structure under different parameters(end face reflectivity and cavity length)are analyzed,the advantages and disadvantages of the existing fiber F-P demodulation methods are discussed,and an improved cross-correlation demodulation algorithm is proposed.(2)Based on the principles of elasticity and optical fiber sensing,the sensing element of the optical fiber F-P temperature and pressure integrated sensing probe was designed,and the sensing performance of the sensing element under different materials and sizes was analyzed by simulation,and the sensing performance of the sensing element was further optimized.Structural parameters of the element.The fabrication process of the sensing element and the encapsulation method of the fiber F-P integrated temperature and pressure sensing probe were studied.(3)Aiming at the huge computational complexity of the traditional CrossCorrelation Demodulation(CCD)algorithm,a combined algorithm of Fibonacci-CCD is proposed.The normalized spectral signal of the sensing probe is obtained by cubic spline interpolation,wavelet denoising and Hilbert transform,and the spectra of the two sensitive cavities,pressure and temperature,are extracted by band-pass filter,and then the cavity length is accurately calculated.On the basis of the CCD algorithm,the Fibonacci search method is used to search for the maximum correlation coefficient,which improves the demodulation efficiency of the algorithm and realizes the fast and high-precision demodulation of the spectral signal of the sensing probe.(4)A set of optical fiber F-P temperature and pressure integrated sensing system was built,and the performance of the sensing probe was experimentally studied.The results show that the optical fiber F-P temperature and pressure integrated sensing probe can accurately measure pressure and temperature simultaneously.The pressure sensitivity in the 0～14 k Pa pressure working range is 3.6581 nm/k Pa,and the maximum error is 0.043 k Pa;the temperature sensitivity in the 35～50 ℃ temperature working range is 1.7543 nm/℃,and the maximum error is 0.2 ℃.