Fiber Weak Magnetic Field Sensor Technology

The magnetic field measurement technology is applied in industry, agriculture, national defence, biology, medicine, cosmic aviation, etc department. In this paper, the research and current status of development of optical fiber weak magnetic field sensor are outlined. The magnetostriction theory of amorphous alloy is introduced, the calculated formulas of magnetic field and magnetostriction is investgated and verified by experiment when considering magnetic field, stress and measurement direction. A optical fiber weak magnetic field sensor system based on Mach-Zehnder interferometer is established. The theory of Mach-Zehnder interferometer, magnetostrictive transducer, high frequency modulation, the minimum magnetic field that can be measured in theory is analyzed. The principle and application confines of the pick-pick theory which used in the magnetic field measurement is introduced, also the error factors are discussed. The system is delved and the three-point methodology used in signal processing is expounded. In order to achieve the three-point methodology measurement, a program which can be used under windows98 is compiled by mean of Borland C++ Builder5.O, as a result, the response time is shortened , the dynamical range of measurement is enlarged and the advantage and fault of the three-point methodology is analyzed. In order to measure magnetic field, the theory that using genetic algorithm to fit the output signal of the sensor system is demonstrated first. In the interest of the model and simulation of the sensor system, a program is designed. A lot of experiment results that it is workable applying genetic algorithm to optical fiber weak magnetic field sensor system. The research in this paper founds certain theory basis for the practical system in future.