Research On Optical Fiber Sensing Technology Based On Special Microstructure Fiber And Cone Structure

In recent years,with the rapid development of optical fiber manufacturing technology,the closely related optical fiber sensing technology has gradually entered the sight of many researchers.Optical fiber sensors have been widely used in various industries due to their small structure,light weight,and anti-electromagnetic interference characteristics,such as civil engineering,chemistry and chemical engineering,clinical medicine,and power system monitoring.Among them,the mode interference optical fiber sensor shows great research advantages in the optical fiber sensor due to its flexibility,compactness and versatility.At present,on the basis of devoting to improving the optical fiber structure and improving the sensitivity of optical fiber sensors,people are also focusing on how to make full use of the characteristics of optical fibers to achieve multi-parameter measurement,which is also one of the research hotspots of optical fiber sensors.The research of this thesis is mainly based on the principle of fiber inline mode interference,combining the new cone structure with the single-mode fiber and special microstructure optical fiber,and using different optical transmission mechanisms to design a new type of optical fiber sensing structure,and using different optical transmission mechanisms to design a new type of optical fiber sensing structure,achieving a compact,Miniaturization and high sensitivity optical fiber dual parameter measurement sensor.The main research contents of the paper are as follows:（1）On the basis of fully understanding the research status at home and abroad,the principle of the fiber in-line Mach-Zehnder mode interferometer is deeply analyzed,and the three factors affecting the spectral quality of the sensor are discussed,and from the principle of temperature,strain,curvature and magnetic field sensing,the feasibility of realizing dual-parameter measurement is analyzed.（2）Using low-cost single-mode fiber misalignment fusion to realize the J-taper structure,and by analyzing the influence of different sensing lengths and misalignment distances on the spectral quality,the best fiber preparation parameters are selected;with the method of wavelength demodulation got the highest sensitivity 77pm/℃and 20.04pm/μεof temperature and axial strain respectively.The sensitivity matrix is used to realize the dual-parameter measurement of temperature and strain,and the measurement resolution of temperature and strain reached±0.56℃and±7.9με,respectively.Also,the optical fiber sensor and the magnetic fluid are combined to make a magnetic field sensor head,and the magnetic field sensitivity is up to-0.032d B/Oe.（3）A new type of special microstructure optical fiber for single-hole twin suspended core fiber（SHTSCF）is used to make the fiber sensor,and the length of the sensing area is5.2mm.The hollow core anti-resonance effect is combined with the fiber in-line MZ mode interference effect,and the spectrum is optimized by making an S-cone structure and improving parameters,and using Gaussian fitting to track the resonance wavelength of the anti-resonance effect.The curvature sensitivity of-7.23d B/m^-1 is obtained by intensity demodulation of the resonant wavelength of the anti-resonance effect,and the temperature sensitivity of 28.8 pm/℃is obtained by using wavelength demodulation for the in-line MZ interference wavelength,dual-parameter measurement of strain and temperature is realized.The temperature cross sensitivity of this sensor during curvature measurement is0.0024 m^-1/℃.