Theoretical And Experimental Study Of Distributed Stress Sensing Based On Polarization-maintaining Fiber

White light interference polarization coupling measurement system based on polarization-maintaining fiber(PMF)has the advantages of high dynamic range,high spatial resolution,and high accuracy,and can realize the stress measurement of the PMF.Relevant studies have shown that white light interferometry systems based on PMF can be applied to the field of stress sensing,but the theoretical and experimental research on distributed stress sensing is not yet specific enough.Therefore,in this paper,theoretical derivation and experimental research are carried out for distributed stress measurement of PMF.The main work of this paper is as follows:1.By establishing the distributed stress sensing model of the PMF,under the two conditions of transverse stress and hoop stress,the stress-polarization coupling theory based on the PMF is deduced.Based on the finite element theory,the stress sensing performance of the PMF is analyzed.Under the same stress,the coupling strength under the transverse stress is 10~6 of the coupling intensity under the hoop stress.Distributed sensing simulation analysis of the lateral stress and hoop stress acting on the PMF,the lateral stress resolution is less than 0.5 N/mm,and the hoop stress resolution is less than0.1 MPa,which verifies that the PMF has the ability of distributed sensing,to provide a theoretical basis for subsequent experimental research.2.A spatial optical distributed stress sensing measurement system was built,and two stress sensing elements were designed for force conduction.The experimental sensitivity was 0.372 dB/KPa and 0.602 dB/KPa respectively,and the lateral stress distribution measurement of 0-12 KPa was carried out.Experiments to verify the feasibility of distributed lateral stress sensing.An all PMF distributed stress sensing measurement system was built,and the hoop stress sensing experiment of 0-0.29 MPa was carried out,and the distributed hoop stress measurement in the range of 0-0.2 MPa was realized by using two sections of PMF to verify the hoop stress.The coupling strength of the PMF has a Sine function variation trend under the action of stress.Finally,the experiment of the combined effect of transverse stress and hoop stress sensing is carried out,which verifies the distributed stress sensing theory of PMF.3.Based on the distributed stress sensing theory of polarization-maintaining fibers,the polarization extinction ratio(PER)and the crosstalk of the pigtail are calculated by setting the dynamic threshold and dynamic step size,and superimposing the coupling points of the Y-waveguide and the pigtail respectively.Efficient signal denoising is performed by Complete Ensemble Empirical Mode Decomposition with Adaptive Noise.The PER measured after denoising is in good agreement with the measured value of the PER meter,the accuracy can reach 0.1 dB,and the pigtail crosstalk is calculated as-43.77 dB.A plan for extending the distance of the PMF distributed stress sensing measurement system is proposed to increase the measurement range to 9.78 km.