Vector Magnetic Field Sensing Investigation Based on Integrated Side-Polished Eccentric-Core Fiber and Magnetic Fluid

This article proposes and demonstrates a magnetic fluid (MF)-coated optical fiber vector magnetic field sensor by fusing a section of side-polished eccentric-core fiber (ECF) between two sections of single-mode fibers. Owing to the distinctive internal structural asymmetry of the ECF, and through the side-polishing process to remove a portion of the cladding, the interaction between the evanescent field and the surrounding MF is enhanced, thereby improving the sensor’s sensitivity. The experimental results show that the sensor’s sensitivity depends on the side-polishing depth and eccentricity of the ECF. When the eccentricity of the ECF is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$20~\mu $ </tex-math></inline-formula>m and the side-polishing depth is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10.40~\mu $ </tex-math></inline-formula>m, the intensity sensitivity of 0.791 dB/mT and 569 pm/mT and the direction sensitivity of 517 pm/° are obtained. The proposed all-optical fiber magnetic field sensor has the advantages of compact structure, low cost, and convenient manufacture.