Abstract
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.
Highlights
Optical fiber sensors based on intensity modulation or phase modulation have many problems
Several factors, such as intensity fluctuation of light source, loss of optical coupler, scattering and absorption effects, and so on, will have negative impacts on the measurement accuracy of an optical fiber sensors based on intensity modulation
The central wavelength and bandwidth Δλbw of the reflected light by chirped fiber Bragg grating (FBG) is measured at different magnetic strength by using a spectrum analyzer, and the magnetic induction intensity of the field can be calculated from equation (15)
Summary
With the development of optical fiber sensing technology, optical fiber sensors have increasingly become the research focus. At present, optical fiber sensors based on intensity modulation or phase modulation have many problems. As FBG is capable to reflect light in specific wavelength, FBG array could encode optical pulse signals in time domain and frequency domain, and is easier to accomplish Wavelength Division Multiplex (WDM). These signals can be written directly into the optical fiber without changing its diameter, which makes the fiber compatible with many small diameter detectors. The FBG sensor is based on Bragg wavelength drift which has the problem in cross-sensitivity of strain and temperature.. In order to simplify the structure of the sensing system, a novel chirped FBG17,18 magnetic field sensor that is not sensitive to temperature variation, by which the cross-sensitivity of strain and temperature would be eliminated, is developed in our study
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
