Magnetic Field Sensing Based on Magnetic-Fluid-Clad Fiber-Optic Structure With Up-Tapered Joints

A kind of magnetic field sensor based on mode interference effect is proposed. The sensing arm consists of two special up-tapered joints formed on the traditional single-mode fiber by fusion tapering technique. Magnetic fluid is used as the cladding of the structure. The interference valley wavelength or the transmission loss of the sensing structure is sensitive to the external magnetic field, which is utilized for magnetic field sensing. The sensitivity of shift of interference valley wavelength with magnetic field can be up to 325.3 pm/mT in the range of 0–16 mT. The variation of transmission loss at valley wavelength with magnetic field has a sensitivity of $-$0.2121 dB/mT in the range of 2–30 mT.