Fiber Microcavity Magnetic Field Vector Sensor With Temperature Compensation Using a FBG

A magnetic fluid filled fiber microcavity magnetic field vector sensor cascaded with a FBG is proposed for simultaneous measurement of magnetic field and temperature. The microcavity Mach-Zehnder interferometer (MZI) structure is formed through the splicing three sections of single-mode fibers with a large lateral offset. Due to the axial asymmetry structure, the microcavity MZI can recognize the direction change of magnetic field and realize vector sensing. The maximum sensitivity to magnetic field direction is −0.275 nm/°. Through monitoring the spectral shifts of the MZI and FBG, we can measure magnetic field and temperature simultaneously. The sensor exhibits the magnetic field and temperature sensitivities of −2.144 nm/mT in the range of 10 to 15 mT and 1.751 nm/°C in the range of $22.5~^{\circ }$ C to $55~^{\circ }$ C. Additionally, the temperature sensitivity of FBG is 0.0098 nm/°C. The proposed fiber magnetic field vector sensor offers advantages such as high sensitivity, compact structure and easy to fabrication, making it highly promising in the applications of magnetic field sensing.