Dual-tapered fiber Mach–Zehnder interferometric magnetic field sensor based on magnetic fluid

Detecting the magnetic field of the electrical equipment is crucial. To achieve high-sensitivity detection of magnetic fields, this paper presents an innovative high-sensitivity magnetic field sensor that utilizes an all-fiber Mach–Zehnder (MZ) interferometer constructed from standard single-mode fibers (SMFs). The core of the interferometer comprises two concatenated tapered optical fibers immersed in magnetic fluid (MF). The sensor operates on the principle that the refractive index (RI) of the MF varies with changes in magnetic flux density. This variation in the RI causes a shift in the attenuation peak wavelength of the interference observed in the transmission spectrum. To analyze light propagation within this dual-tapered fiber MZ interferometer, numerical simulations were conducted using the beam propagation method (BPM). These simulations were critical in predicting the sensor's performance and optimizing its design. Following the simulations, a series of experiments were performed to evaluate the sensor's response to different magnetic flux densities. The experimental results demonstrated a high sensitivity of 0.095 nm/mT within a magnetic flux density range of 0–20 mT. This level of sensitivity, coupled with the low cost and simplicity of the all-fiber construction, makes the proposed sensor highly suitable for practical applications, particularly in the monitoring of electric equipment. Its ability to provide precise and real-time measurements of magnetic fields can significantly enhance the reliability and safety of electrical systems. The research findings suggest that this sensor could be a valuable tool in various industrial and technological fields, where accurate magnetic field detection is crucial.