Magnetic field vector sensor based on a cascaded structure of core-offset Fabry–Perot interferometer and a magnetic fluid infiltrated glass capillary

A magnetic field vector sensor based on a cascaded structure composed of a core-offset Fabry–Perot interferometer (FPI) and a magnetic fluid (MF) infiltrated glass capillary (GC) is proposed and demonstrated. An air-gap FPI with a cavity length of 85 µm is formed by core-offset fusing two single-mode fibers separated by a short hollow-core fiber (HCF). The FPI is cascaded with an MF-infiltrated GC. By the directional bending effect of the core-offset FPI caused by magnetic field force on the MF-filtrated GC, the magnetic field can be monitored in strength and direction. Experimental results show that, in a magnetic field strength range of 0–9 mT, the sensor can achieve sensitivities of 4.63 and 4.25 pm/mT in two opposite directions.