Fiber Laser Magnetic Field Sensor Based On Ampere Force And Magnetic Force

Magnetic field is very important in various fields.Detection of magnetic field has always been a research hotspot worldwide,attracting attentions of many countries and research institutions.Compared with magnetic field sensors in traditional electrical fields,optical fiber magnetic field sensors have advantages of low loss,light weight,and protection from electromagnetic interference.This makes optical fiber magnetic field sensors have unique advantages in magnetic field measurement in applications with complicated electromagnetic environment.Fiber optic magnetic field sensors have been widely used in a number of areas,such as navigation,seabed detection,health care,biotherapy,current detection,artificial intelligence,smart transportation and so on.However,in practice,optical fiber magnetic field sensors are often susceptible to interference from external environment,and hence the performance of sensors is impacted by many factors and the accuracy and reliability of measurement is degraded.Therefore,suppression of interference is of great importance to magnetic field sensors.For fiber-optic magnetic field sensors,this interference may come from temperature changes,vibration and other environmental disturbances,and these interferences are mainly manifested in low-frequency bands.Therefore,sensors that measure magnetic fields directly in the low-frequency band are susceptible to environmental interference,which results in serious restriction on measurement of stationary and low-frequency magnetic field.Motivated by this practical requirement,this dissertation studies suppression of low-frequency noise and interference to improve the sensitivity and reliability of fiber-optic magnetic field sensors through conversion of stationary magnetic field to alternative magnetic field.The main research work of this dissertation is as follows:1)A scheme based on Ampere force and orthogonal dual-frequency fiber grating laser is proposed with its working principle elaborated.Based on alternative Ampere force generated by alternative current in a magnetic field,measurement of a stationary magnetic field can be worked in a high frequency band and hence low-frequency environmental interference can be eliminated,making sensitivity improved and measurement more reliable.2)Miniature package of fiber-optic magnetic field sensor based on Ampere force and orthogonal dual-frequency fiber grating laser has been studied through experiments.The sensitivity of the sensor can be optimized by tuning the alternating frequency of Ampere force to the resonance peak at a certain frequency of the package.In experiments,a maximum response of 35.21 k Hz/k Gs is obtained.3)The response of orthogonal dual-frequency fiber grating laser to alternative gradient magnetic field is studied and resonance of magnetic force is observed.A measurement to a resonance peak at 500 k Hz is studied in experiments which gives a resonance spectral width of about 4.5 k Hz.The resonance of this magnetic force can be utilized to improve the sensitivity of magnetic field measurement and suppression of interference.