Research On Optical Fiber Magnetic Field Sensor Based On Optical Resonancr

Magnetic field sensors have important application values in the fields of geophysical surveying and navigation,military equipment applications,biomedical sensing,and aerospace field.Especially with the development of human-machine exchange technology,biological imaging,and unmanned monitoring equipment,this puts forward new application requirements for magnetic field sensors such as high sensitivity,wearability,low cost,miniaturization,high integration,and high monitoring accuracy,which have aroused widespread attention and research interest of scholars.The existing commercial magnetic field sensors are mostly electrical sensors based on Hall-effect,fluxgate,giant magnetoresistive,and superconducting quantum interference.The type of magnetic field sensor has problems such as complex structure,temperature control protection,and susceptibility to electromagnetic interference,which makes it difficult to meet the application requirements of special environments.Various type of optical fiber sensor has the advantages of simple production,low cost,high sensitivity,small size,compact and lightweight structure,easy integration and multiplexing,and multi-parameter in-situ sensing,therefore,it has shown good application potential in magnetic field detection and other fields,and it also be regarded as a good choice for a new generation of comprehensive monitoring system of magnetic field environment.In this paper,we use COMSOL Multiphysics finite element analysis software to design two fiber optic magnetic field sensors based on optical resonance for the new application requirements of magnetic field sensors.The main research contents are as follows:1.First,the research progress of optical fiber sensing technology in magnetic field sensors is introduced in detail,and the advantages and disadvantages of sensor structures such as Faraday effect type,magnetostrictive effect type,magnetic fluid type and optical resonance effect optical fiber magnetic field sensor are compared and summarized.2.The basic optical properties and main characteristic parameters of the whispering gallery mode resonance and the basic optical properties and dispersion relations of surface plasmons are theoretically deduced and explained,and the composition of the new material magnetic fluid And the relationship between the properties and the refractive index of the magnetic fluid and the change of the magnetic field.Then,the finite element analysis method,scattering boundary conditions and perfect matching layer are introduced.3.A magnetic field sensor based on side-polished fiber and microspheres is proposed.By adding optical fiber microspheres,light propagates through the near-field coupling to the microspheres and directly arouse the whispering gallery modes.The resonant light in the microcavity has a very narrow spectral line width,which greatly improves the sensor Quality factor(Q)and figure of merit(FOM).The simulation results show that the magnetic field sensor has a strength sensitivity of up to 0.75 d B/Oe and the Q value of the microsphere cavity up to 2.5x10~4,which has a refractive index sensitivity of 125 nm/RIU,and a maximum FOM of 2.5x10~3.Compared with the traditional magnetic fluid magnetic field sensor,the proposed sensor has a simple structure,low production cost,high Q-factor and high FOM.It has potential application prospects in developing magnetic field sensors compatible with high-sensitivity sensing and high-precision detection.4.A new photonic crystal fiber magnetic field sensor based on surface plasmon resonance(SPR)is proposed.The presence of metal will stimulate SPR.The sensitivity of the magnetic field sensor can be improved by stimulating SPR.The simulation results show that the sensor is very sensitive to changes in refractive index.When gold-plated and metal thickness h=50nm,the refractive index sensitivity is 4125 nm/RIU,when silver-plated and h=50nm,the refractive index sensitivity is 4755 nm/RIU,and the highest magnetic field sensitivity can reach 61.25 pm/Oe.