Fiber-Optic Vector-Magnetic-Field Sensor Based on Gold-Clad Bent Multimode Fiber and Magnetic Fluid Materials

Abstract

A kind of bent multimode fiber (MMF) vector magnetic sensor based on surface plasmon resonance (SPR) was proposed. By plating gold film on the curved part of the bent multimode fiber, the surface plasmon mode (SPM) was excited via a whispering gallery mode (WGM). Fabricating the structure only required bending the fiber and plating it with gold, which perfectly ensured the integrity of the fiber and made it more robust compared with other structures. The sensor used magnetic fluid (MF) as the magnetically sensitive material. Through monitoring the shift of the surface plasmon resonance dip, the as-fabricated sensor not only had a high magnetic field intensity sensitivity of 9749 pm/mT but could also measure the direction of a magnetic field with a high sensitivity of 546.5 pm/°. The additional advantages of the proposed sensor lay in its easy fabrication and good integrity, which make it attractive in the field of vector-magnetic-field sensing.

Research Progress on Magneto-Refractive Magnetic Field Fiber Sensors

“…Macro-bending fiber has a proper bending size, where light in the core overflows into the cladding at a large curvature point, resulting in the generation of cladding modes. On the basis of the sensor with macro-bending fiber proposed by Li et al [ 74 ], Liu et al [ 75 ] deposited gold films on the surface of the fiber by magnetron sputtering ( Figure 9 b), so that the SPR effect was stimulated. With a high wavelength sensitivity of 974.9 pm/Oe and a good vector property of 546.5 pm/°, this sensor is simple, low cost, and convenient for fabrication.…”

“… Magnetic fiber sensors based on ( a ) a side-polished fiber [ 71 ] and ( b ) a U-shape macro-bending fiber (reprinted with permission from Ref. [ 75 ], 2022, MDPI). …”