Intensity-modulated magnetic field sensor based on fiber Bragg grating

A magnetic field sensor based on the chirp effect of fiber Bragg gratings (FBG) was devised, and the relationship between the reflectance spectrum bandwidth and the magnetic induction intensity is deduced. The magnetic force from an energized spiral coil acts on the disk-shaped soft iron in the magnetic field to cause the deformation of the rectangular cantilever beam, which results in the bandwidth change of the reflection spectrum of the FBG adhered to the side of the cantilever. The magnetic strength can be obtained by detecting the bandwidth change of the reflection spectrum of the FBG with a spectrum analyzer. While the spectral analyzer resolution is 0.001nm, the measuring range of magnetic induction intensity is 6- 70mT. The experimental results demonstrate that the bandwidth variation of the reflection spectrum of the FBG is not sensitive to temperature changes. The 3db bandwidth changes less than 8 pm as the temperature varies from 0°C to 45°C. The experimental results are consistent with the theoretical analysis, indicating that the scheme is feasible and practical.