Intensity-demodulated fiber-optic vector magnetic field sensor based on fiber-optic evanescent field

A high-sensitivity intensity-demodulated fiber-optic evanescent field sensor is proposed for vector magnetic field measurement. The structure was fabricated by bending a section of single mode fiber into a U shape under the flame of alcohol burner, and then coated with magnetic fluid. By bending the fiber into a U shape, a non-centrosymmetric fiber-optic evanescent field is distributed on the cross section of fiber. Combing with the magnetic-field-dependent anisotropy of magnetic fluid, a high intensity sensitivity of 2.481 dB/mT and a high direction sensitivity of 0.182 dB/° were obtained. Due to the simple structure, high sensitivity and low cost, the proposed fiber-optic sensor has potential application in the vehicle navigation, aviation, and biomedical fields.