IEEE Sensors Journal | 2021
Multipoint Magnetic Field Measurement Based on Magnetic Fluid and FSI-FLRD
Abstract
We present a multipoint fiber magnetic field sensing system based on magnetic fluid (MF) and frequency-shifted interferometry fiber loop ringdown (FSI-FLRD). This system contains a number of cascaded sensing channels, and shares a common continuous-wave light source and slow electronics instead of a pulsed light source and high-speed electron devices as required in traditional multichannel FLRD techniques. Each sensing channel is formed by incorporating an MF-coated etched fiber as the sensing head inside a fiber ringdown loop. Each sensing head is mounted on a temperature control device. We experimentally fabricated a dual-channel FSI-FLRD magnetic field sensing system. First the system’s temperature response was investigated, which indicates the MF-based sensing heads had temperature cross sensitivity. Then after keeping the temperature at 20 °C for improving testing accuracy and applying different magnetic fields, the two sensing channels were separately shown to have sensitivities of <inline-formula> <tex-math notation= LaTeX >$- 9.38\\times 10 ^{-5}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation= LaTeX >$- 2.28\\times 10 ^{-5}$ </tex-math></inline-formula> /(km<inline-formula> <tex-math notation= LaTeX >$\\cdot $ </tex-math></inline-formula>Oe) with a linear response in the range of 221–721 Oe. The obtained sensing channel stabilities were respectively 0.02% and 0.04%, which enhance more than one order of magnitude compared with those of most conventional FLRD techniques.