Optic-fiber vector magnetic field sensor utilizing magneto-shape effect of magnetic fluid

In this work, an optic-fiber sensor utilizing magneto-shape effect of magnetic fluid (MF) has been put forward to measure magnetic field direction. MF magneto-shape effect has been presented, simulated and verified through experiments as a magneto-optical effect. The sensor consists of a capillary glass tube, two single-mode fibers (SMFs) and MF. The interface between MF and air is concave because the glass tube is attractive to MF. As magnetic field rises, the concavity degree becomes more obvious, in other words, edge length of MF cavity is extended and central length of cavity is shortened. The interference wavelength of sensor will change with magnetic field, so as to achieve the purpose of monitoring magnetic field. The phenomenon is defined as the magneto-shape effect of MF. Due to the magnetic field direction dependence of pressure difference between the MF and air, the magneto-shape effect of MF has different perception of axial magnetic field and radial magnetic field, realizing vector magnetic field measurement. Results of experiment are shown as follows: the sensor can easily react to field strength and orientation. The wavelength shows the shape of number “8″ with magnetic field direction changing. The field sensitivity reaches up to 296.1 pm/Gs from 22.6 Gs to 121.8 Gs in the axial field. Moreover, direction sensitivity reaches 311.6 pm/° at 104.4 Gs. The wavelength shift in the axial direction is 25.5 times higher than that of the radial direction. The presented sensing structure could monitor vector magnetic field without constructing a non-circular symmetrical structure. The proposed sensing structure is provided with characteristics of simple to make, highly-sensitive and little fabrication consumption. It possesses potential applications in electronic power industry and aerospace.