Magnetic sensing technology of fiber optic interferometer based on magnetic fluid: A review

The magnetic field is crucial in fields like geography, industrial production and medical treatment. The requirement for magnetic field sensors is increasing, thus a class of high-precision, ultra-sensitive, low-cost sensors is needed. Fiber optic magnetic field sensors have attracted much attention because of their high sensitivity, small size, good portability, corrosion resistance and long-distance transmission. Magnetic fluid is easily combined with fiber optic sensors because of its unique magneto-optic property. Among many fiber optic sensors, the fiber optic interferometer has been favored by researchers because of its simple manufacture, flexible design and high precision. Four different types of fiber optic sensors: Mach-Zehnder interferometer (MZI), Michelson interferometer (MI), Fabry-Perot interferometer (FPI) and Sagnac interferometer (SI)—are summarized in this work, and the technological challenges are then highlighted. Finally, the research direction and challenge of fiber optic magnetic interferometer with the magnetic fluid has been prospected. The findings demonstrate the tremendous potential for magnetic sensing offered by the fiber optic interferometer and magnetic fluid combination.