An intensity-modulated and large bandwidth magnetic field sensor based on a tapered fiber Bragg grating

摘要

An intensity-modulated and large bandwidth magnetic field fiber sensor with tapered fiber Bragg grating (TFBG) had been proposed and demonstrated by experiments. Fiber Bragg grating (FBG) was created into a tapered fiber to form TFBG, which not only had powerful evanescent field but also possessed large bandwidth for the fiber refractive index decreased along the tapered region. The TFBG inserted into a 0.3 mm diameter glass tube which was filled with the magnetic-fluid (MF), and then this structure was packaged to form an integration magneticfield fiber sensor. The refractive index of the MF will changed under varied magnetic-field, so the reflection spectral of the sensor should have a corresponding changed with the magnetic-field changed due to the tunable refractive index of MF. We designed the experiments and tested the sensor. The experimental results show that a nonlinear curve is between light intensity variation and changed MF intensity variation, the uniformity fitting degrees are 0.999 and 0.996 among the magnetic field increased and declined and the maximum sensitivity is -0.1933 dB/Oe and -0.1533 dB/Oe, respectively. Moreover, we find magnetic hysteresis has no obvious affection on the magnetic vectors (0 and 180 deg). This proposed magnetic-field sensor has the benefits of no direction disturbance, large bandwidth, high sensitivity, and integration.