Low-Cost Magneto-Optic Sensor Based on Tapered Fiber and Distributed Sensing Concept

In this letter, we present a magnetic field sensor with a noise equivalent field of 500 nT based on a tapered fiber in a magnetic fluid (Fe
₃
O
₄
nanoparticles dispersed in the deionized water). This sensitivity, which is three orders of magnitude better than the previously demonstrated tapered sensors, is achieved by biasing the fluid material with a ≈1-mT magnetic field. In addition, application of an optical modulator and an auto-balanced synchronized detector increased the sensor output signal-to-noise ratio significantly. Furthermore, a novel method is presented to employ the proposed sensor in a distributed scheme.