Research On Key Technologies Of Polarization Maintaining Fiber Temperature Sensing Based On Polarization Interference

Accurate temperature measurement is of great significance in the fields of healthcare,industrial and agricultural production,and modernization of national defense.The polarization maintaining fiber temperature sensor based on polarization interference has become a research hotspot in the field of fiber temperature sensing due to its advantages of high sensitivity,simple structure,low cost,fast response,lightweight,and easy to remote monitoring.However,at present,the measurement range and accuracy of such temperature sensor cannot meet the increasing requirements for temperature monitoring.Therefore,in order to solve the problem of this sensor,in this thesis,the corresponding theoretical analysis are performed,specific solutions are proposed,and experimental verification are conducted.The main research contents and results are as follows:1.Theoretical simulation analysis of polarization maintaining fiber temperature sensors based on polarization interference is conducted.Specifically,the stress distribution,birefringence distribution,and temperature characteristics of Panda type polarization maintaining fiber(PMF)are studied.Furthermore,Jones matrix models are established for the transmissive and reflective polarization interferometers,respectively,and the influence of key parameters of the sensor on the output spectrum are also explored.2.When the traditional dip wavelength tracking method is used to demodulate the temperature,the sensing range of the polarization interferometer will be limited by the periodicity of the spectrum.In order to solve this problem,the least squares method for demodulating the birefringence of PMF for temperature sensing is proposed.By analyzing the demodulation principle and carrying out experimental research,when the free spectral range of polarization interference is 18 nm,the temperature measurement range has been relatively increased by 5.5 times.3.The Polarization interferometer with current temperature sensitivity cannot be used for ultra-high precision temperature monitoring.In order to solve this problem,a cascaded PMF-Fabry Perot sensing structure is proposed,and an ultra-highly sensitive temperature measurement system based on the Vernier effect is established.The sensing system finally achieves a temperature sensitivity of up to-31.4 nm/?,which is about 17.34 times larger than a separate PMF temperature sensor,and shows good repeatability and stability.In addition,the initial state of the sensor can be tuned by loading strains on the Fabry Perot cavity,so that the maximum sensing range is available at any initial temperature.4.In order to make the traditional temperature measurement system more practical and portable,a miniaturized prototype system based on the tunable laser and photodetector is designed.The corresponding hardware selection and software programming are completed.Finally,a stable and reliable automatic temperature measurement was finally achieved.