IEEE Photon. Tech. Lett. 26, 217–219 (2014)

Researchers at Northeastern University in Shenyang, China, have demonstrated a compact optical-based magnetic-field sensor that has a high sensitivity of 0.0431 nm Gs−1. It consists of an optical-fibre Fabry–Pérot interferometer whose cavity is filled with a magnetic fluid — a stable colloidal suspension of single-domain magnetic nanoparticles uniformly distributed in a carrier fluid by a surfactant. The refractive index of the magnetic fluid was found to increase linearly with increasing magnetic field strength, enabling it to be used in the magnetic-field sensor with optical read-out. This latest design is said to be simple, compact, easy to fabricate and yet provides a high stability and a high sensitivity. Further work is needed, however, to address the temperature dependence and packaging of this sensor.