Research On Magnetic Field Vector Measurement Based On Fiber Mounted Magneto-optic Probe

Electromagnetic detection technology is one of the most important research fields in both civilian and military. The conventional electronical detecting system which is usually based on an active metallic cable, may disturb the distribution of the magnetic field to be measured and degrade the detecting accuracy. While the fiber sensor based on a magneto-optic (MO) crystal has far-ranging applied space in the measurement of magnetic field because of its particular characteristics such as invasiveness to electromagnetic field, high sensitivity, high spatial resoluton, wide dynamic range and so on.In this paper, a convenient scheme for three-dimensional magnetic field vector measurement using a fiber mounted MO probe is proposed, which can detect the intensity and the direction of the longitudinal and transverse fields simultaneously. When a linearly polarized light passes through a MO crystal placed in a magnetic field, the polarization state of the optical beam will change due to the amplitude variation and the phase shift resulted from the magneto-birefringence effect and the Faraday effect. By detecting the polarization state variation of the optical beam, the magnetic field vector measurement can be achieved.Before the experiments, a high speed polarization controlling system based on TI’s TMS320F2812chip is designed because of the strict requirement of the input linearly polarized polarization and the precise requiremnt of the output polarization measurement. Then based on the theoretical research, the MO probe implementation in an all-fiber-coupled optical network is introduced. The accuracy and feasibility of the magnetic field measurement using a fiber mounted MO probe are demonstrated by detecting the intensity of the output light directly. The experiment based on the modulation-demodulation technology is also conducted to demonstrate that such a method can improve the sensitivity effectively. In the end, it’s demonstrated that it’s feasible to achieve the magnetic field vector measurement using a fiber mounted magneto-optic probe by the mathematical deduction and simulation analysis. Moreover, the proposed system is investigated numerically and the calibration process is described.