Transmissive optical fiber magnetic field sensor based on ferrofluids

A compact optical fiber magnetic field sensor is reported which relies on the magnetic field induced displacement of a ferrofluid lying in the gap between two single mode optical fibers (SMFs) that are aligned face to face. The ferrofluid displacement alters the coupling of light from the input optical fiber to the output optical fiber. When the applied magnetic field changes from 0 mT to 10 mT the optical attenuation changes from 0 dB to -28 dB