Magnetic field sensor based on asymmetric optical fiber taper and magnetic fluid

• An optical fiber magnetic field sensor was constructed by incorporating magnetic fluid and a core–cladding–mode interferometer.
• The sensing performances of the sensors are controllable by designing the parameters of the asymmetric-tapered structure.
• The sensitivity of sensor with axial offset of 168 μm and taper waist diameter is ∼162.06 pm/mT ranging from 0 to 21.4 mT.

We report an optical fiber magnetic field sensor by merging the advantages of magnetic fluid and a core–cladding–mode interferometer which is directly fabricated on a standard single-mode fiber by using an arc fusion splicing machine. The sensing performances of the sensors are controllable by designing the parameters of the asymmetric-tapered structure. Experimental results show that the sensor with axial offset of 168 μm and taper waist diameter of 45 μm not only has good optical properties but also a relatively high magnetic-field sensitivity of ∼162.06 pm/mT ranging from 0 to 21.4 mT. The proposed sensors would find potential applications in weak magnetic sensing fields.