Vector magnetic field sensor based on U-bent single-mode fiber and magnetic fluid.

A novel, compact, and easy fabrication vector magnetic field sensor has been proposed and investigated. The proposed sensor consists of a U-bent single-mode fiber fixed in a magnetic-fluid-filled vessel. Neither mechanical modification nor additional fiber grating is needed during the sensor fabrication. The results show that the response of magnetic fluid to magnetic field can be used to measure the direction and intensity of magnetic field via whispering gallery modes supported by the U-bent fiber structure with suitable bending radius. The sensitivity of direction is 0.251 nm/°, and the maximum magnetic field intensity sensitivity is 0.517 nm/mT. Besides, the results of this work prove the feasibility for realizing vector magnetic sensors based on other bending structures (such as bending multimode interference, bending SPR structure) in the future.