Investigation of the magnetic field sensing properties of a magnetic fluid clad microfiber knot sensor

The performance of a magnetic fluid clad microfiber knot-based magnetic field sensor was experimentally investigated in the presence of static and dynamic magnetic fields. In addition, the dependence of the sensor response on the orientation of the externally applied magnetic field has been evaluated. The results show that the proposed sensor provides simultaneous measurements of magnetic field strength and orientation by monitoring the resonant wavelength of microfiber knot. When the magnetic field was increased to 220 Gs, the maximum wavelength shift reached nearly 130 pm. To avoid rectification for alternating current magnetic field input, a direct current magnetic field bias was introduced to the sensor. Using this approach, the unipolar response was converted into a bipolar form, which produced an acceptable replica of the input sinusoidal waveform. These results provide great promise for the development of practical magnetic fluid-based fiber-photonic magnetic field devices.