It is suggested and designed to use Terfenol-D magnetostrictive material in a fiber extrinsic F-P interferometric magnetic field sensor. The two reflective end faces of the F-P cavity are, respectively, the copper reflective layer and the fiber end face. As a result, changes of the magnetic field have an impact on the F-P cavity's cavity length, and the environmental magnetic field can be detected by measuring the variation in cavity length. The typical relationship between magnetic field and spectral drift of the sensor is theoretically analyzed. The sensitivity is measured experimentally to be 0.82 nm/mT for a magnetic field intensity of 0 mT to 70 mT at room temperature. The sensor has a compact structure, and the complexity of the low-level interference signal demodulation makes it suitable for use in engineering.
To simplify the structure and improve the sensitivity of the optical fiber Fabry-Perot (FP) magnetic field sensor (MFS),
an optical fiber extrinsic FP interferometric MFS based on Terfenol-D magnetostrictive material (TDMM) was designed
and fabricated. Insert a TDMM with the diameter of 8mm and a length of 30mm into the cavity, and vapor-deposit 20%
aluminum film on one end surface, and vapor-deposit 60% transmission inducing film on the fiber end surface. The two
film layers are used as a FP with the cavity length of 1.7mm. The relationship between spectral drift and magnetic field
sensing was theoretically analyzed. When the magnetic field intensity is 10~30mT, the sensitivity of magnetic field
sensing is 0.081nm/mT and the interference signal extinction ratio is as high as 9dB at room temperature. The sensor is
featured as the interferometric signal demodulation is simple and potentially can be used in engineering field.
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