Magnetic Field Sensing Characteristics Of Tilted Fiber Bragg Gratings Based On Small Angles And Magnetic Fluid

Since the development of magnetic field sensing,the traditional magnetic field sensor is susceptible to electromagnetic interference,and the optical magnetic field sensor based on optical fiber uses optical signal transmission,which has the characteristics of small volume,light weight,simple structure and no influence of electromagnetic interference.The field of detection has shown certain application prospects.With the development of optical fiber fabrication technology,tilted fiber bragg gratings have been widely studied by academic researchers for their unique optical sensing characteristics.The main innovations and research contents of this paper are as follows:(1)The structure of the tilted fiber bragg grating and the phase matching condition of the core mode in different tilt angles are studied,and the resonant wavelengths of different modes are obtained.At the same time,according to the condition of the fiber cladding and the refractive surface of the external environment,the critical angle of the core mode under different coupling modes is calculated.And the effects of the four parameters of the tilt angle ?,the refractive index modulation depth ?neff,the grating length L and the grating period P on the spectral characteristics of the tilted fiber bragg grating are simulated.(2)According to the spectral characteristics of the tilted fiber bragg grating,the appropriate parameters are selected.By analyzing the transmission spectrum characteristics of the tilted fiber bragg grating,the refractive index sensing characteristics of the tilted fiber grating are studied.Firstly,the influence of strain and temperature factors on the transmission spectrum of the tilted fiber bragg gratings is solved.In the strain measurement range of 0??~2000?? and the temperature measurement range is-50°C~150°C,the strain and temperature are simultaneously measured by the two-parameter method.Determine the four coefficients in the two-parameter two-dimensional equation to resolve the cross-sensitivity of strain andtemperature.Secondly,considering the sensitivity of strain and temperature,the coupling efficiency of core mode and cladding mode,bandwidth detection and other factors,the tilted fiber bragg gratings with tilt angle of 4° is selected to study the refractive index sensing characteristics.The relationship between the resonant wavelength and the refractive index of the external environment in each mode is analyzed when the wavelength of the transmission spectrum is 0.01 nm,and the refractive index of the ambient refractive index is in the range of 1 to 1.4.The refractive index of the external environment is determined by detecting the resonant wavelength.Finally,considering that the tilt angle of the tilted fiber grating may be slightly offset during the actual manufacturing process,the influence of the small angle(0.1°)variation on the sensing characteristics of the tilted fiber grating is studied.(3)According to the tunable characteristics of the refractive index of the magnetic fluid,the relationship between the external magnetic field and the refractive index of the magnetic fluid is simulated by using the Langevin function equation.On the basis of the above,combining the sensitivity of the small-angle tilted fiber bragg grating to the refractive index of the external environment and the refractive index tunable characteristics of the magnetic fluid,an optical magnetic field sensor based on a small-angle tilted fiber bragg grating and magnetic fluid is designed.Magnetic fluid is used as the external environment medium for the small-angle tilted fiber bragg grating.The detection of the magnetic field is realized by detecting the resonant wavelength of the cladding mode of the tilted fiber bragg grating.