Dual-Direction Magnetic Field Sensor Based on Core-Offset Microfiber and Ferrofluid

A fiber-optical sensor is proposed for dual-direction magnetic field measurement by cascading an optical microfiber with a core-offset section. Due to the relative direction difference between magnetic field and fiber axis, the refractive index of the magnetic fluid could be tuned accordingly. The transmission spectral characteristics change with the variation of applied magnetic field. Experimental results show that different relative directions turn out different linear responses. When the magnetic field is applied perpendicular or parallel to the fiber axis, the magnetic field sensitivities are -0.02534 and 0.01111 dB/Oe, respectively. The proposed sensor has several advantages, including low cost, ease of fabrication, compact structure, and cost-effective intensity interrogation. It is promising in the measurement of magnetic field vector, as well as multiparameter sensing.