Dual-channel temperature-compensated vector magnetic field sensor based on lab-on-a-fiber-tip

Fiber-optic magnetic field sensors based on magnetic fluid (MF) is encountering with thermal effects and demand for vectorization for several years. A common solution is to use axially processed fiber cascaded with fiber Bragg grating (FBG). However, the length of such sensors is usually in centimeter-level, which restricts the sensing applications in narrow space and gradient field cases. In this work, we present an ultracompact reflection-type dual-channel sensor for vector magnetic field (Channel 1, referred as CH1) and temperature (Channel 2, referred as CH2) monitoring, which is composed of a pair of gold-plated wedge-shaped multimode fiber (MMF) tip and gold-plated multimode-no-core fiber (MNF) tip. The surface plasmon resonance (SPR) effect was adopted. The two sensor probes are coated with magnetic-field-sensitive MF and temperature-sensitive polydimethylsiloxane (PDMS), respectively. The issue of vector magnetic field and temperature cross-sensitivity is tactfully resolved. Importantly, the proposed sensing probes are ultracompact and the spatial resolution is extremely small (615 mu m for CH1 based on wedge-shaped fiber tip and 2mm for CH2 based on MNF), which is very helpful for narrow space and gradient magnetic field detection. The obtained magnetic field intensity sensitivities are 1.10 nm/mT (90 degrees direction) and -0.26 nm/mT (0 degrees direction), and temperature sensitivity is -3.12 nm/degrees C. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement