High sensitivity magnetic sensor by using fiber Bragg grating bonded to magnetic shape memory alloys

In this work, the experimental demonstration of fiber Bragg grating based sensors as magnetic transducers is reported. Up to now, FBGs based magnetic sensors have been proposed by using Terfenol, metallic alloy with a giant magnetostriction coefficient. Here, a novel configuration is proposed employing a new class of magnetic materials, Magnetic Shape Memory alloys (MSMs), instead of Terfenol. This class of material, with a very giant magnetostriction coefficient, changes its shape when magnetic fields are applied. High strain values, up to 10 percent can be obtained with fast response times (less than 1 ms). A fiber Bragg grating has been bonded on a MSM sample and sensor characterization has been carried out. Experimental results and the comparison with Terfenol based FBGs sensors performances are reported, showing, for MSM, a sensitivity expressed as (ΔλB/λ B)/(ΔH/Hm) of 1.1 e-4.