All Polarization-Maintaining Fiber Earth Magnetic Field Sensor

A polarization-maintaing fiber Mach-Zehnder interferometer is made from polarization-maintaing fiber couplers and other polarization-maintaing fiber components.In the sensing arm,a transducer made by polarization-maintaining fiber bonded on a magnetostrictive material is joined. Because of magnetostriction effect,the phase variation in the fiber caused by earth magnetic field is detected.At last,a stable polarization-maintaing fiber earth magnetic field sensing system is set up.The phase response of the system to the varying magnetic field is measured and analyzed,and the frequency response is obtained too,from which an appropriate AC magnetic field used in the next DC magnetic field sensing experiment has been selected.The magnetic field at level of 1 nT can be measured in the experimental system,and the measured results for the earth magnetic fields in different directions agree with the theoretic prediction,which proves that the system can be used in the navigation and orientation fields.