Optical fiber Fabry-Perot cavity interference magnetic field sensor

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.