Magnetic field sensor based on resonant cavity dispersion-frequency mapping of a multi-longitudinal mode fiber laser

A high-sensitivity and compact-size magnetic field sensor based on a multi-longitudinal mode fiber laser is proposed and experimentally demonstrated in this paper. The resonant cavity is composed of two uniform fiber Bragg gratings (FBGs) and a length of Er-doped fiber. A Terfenol-D rod is used as a transducer to stretch the sensing FBG when applying an external magnetic field. Longitudinal mode beat frequency could be generated in the laser and would shift with the deformation of the sensing FBG caused by the external magnetic field. Experimental results show the sensitivity of the proposed sensor is -47.32kHz/mT.