High-Resolution Measurement of Magneto-Shape Effect Based on Fiber Optic Interferometry Ranging

The magneto-shape effect of magnetic fluid (MF) filled in capillary glass tube (CGT) is verified by the optical fiber interferometry ranging under different nanoparticle concentrations and cavity lengths, which has higher resolution compared with the traditional measurement methods. The observation structures of edge and center cavity length of concave are constructed using CGT and single-mode fiber (SMF). The change in center cavity length of MF is mainly used to characterize the magneto-shape effect due to the high resolution of optical fiber interferometry. Eight structures with different cavity lengths are fabricated using MF with magnetic nanoparticles concentrations of 8% and 10%, respectively. The experimental findings indicate that for the MF with nanoparticle concentration of 8%, the average sensitivity of center cavity length is $9.7\times 10^{-{3}}~\mu $ m/Gs in axial field and $4.5\times 10^{-{4}}~\mu $ m/Gs in radial field. For the MF with nanoparticle concentration of 10%, the average sensitivity of center cavity length is $1.6\times 10^{-{2}}~\mu $ m/Gs in axial field and $- 2.1\times 10^{-{3}}~\mu $ m/Gs in radial field. The magnetic flux density resolution of structure is 0.0059 Gs. The influence of cavity length on magneto-shape effect is relatively small in axial field while shortening the cavity length can enhance the magneto-shape effect on the center of concave surface in radial field. Improving the nanoparticle concentration helps enhance the magneto-shape effect.