Design And Experimental Study Of Optical Fiber Weak Magnetic Sensing System

In recent years,the development of weak magnetic measurement technology is very rapid.It is used widely in military anti-submarine,bio-medical,space exploration,mineral exploration,geological survey and many other fields.With the continuous development of new theories,micro-nano machining and micro-system integration,miniaturization,low power consumption and system integration have become gradually the development trend of weak magnetic field measurement technology.In this paper,combining the magnetic field measurement technology based on atomic spin precession theory and the high-precision measurement advantage of optical fiber sensing technology,a fiber optic weak magnetic field sensor structure based on circular polarization detection is designed and studied in depth.The main research contents include:Firstly,the research background and significance of the project are introduced,several methods of measuring weak magnetic field are summarized,and the research status and development trend of atomic magnetometer at home and abroad are introduced briefly.Secondly,the basic principle of weak magnetic field measurement based on atomic spin precession is introduced,and the energy level structure of cesium metal atom is analyzed.The physical process that alkali metal atoms is polarized by pumped light is introduced in detail,and the relationship between optical rotation angle and magnetic field is analyzed theoretically.Thirdly,a scheme of optical fiber weak magnetic field measurement is designed.The principle of detecting optical rotation angle based on circularly polarized light is analyzed briefly,and the relation between the output light intensity and optical rotation angle is obtained through theoretical analysis.The effect of the core diameter of the hollow photonic crystal fiber atom gas chamber on the collision relaxation between the atom and the wall is analyzed by simulation,and a kind of alkali metal atom gas chamber combining the fiber and the glass tube is designed and fabricated.Finally,in order to increase the number density of cesium atoms,a heating system of atomic gas chamber based on high frequency alternating current was designed and manufactured.A weak magnetic field measurement system based on circularly polarized light is built,the weak magnetic field measurement experiment was carried out,and the experimental results are analyzed.