A high-sensitivity optical fiber dual-direction weak magnetic field sensor based on a structural modulated ultralong period microfiber grating (SULPMG) is proposed. The SULPMG was fabricated by an electric arc discharge and flame-heating drawing method, and the sensor was fabricated by cascading the SULPMG with a core offset section. By tuning the direction of an applied magnetic field, the refractive index of a magnetic fluid (MF) can be tuned accordingly. The transmission spectral response of the proposed sensor was measured and analyzed. For the weak magnetic field intensity range from 0 mT to 7 mT, the obtained magnetic field sensitivity is −1.759 nm/mT and 1.082 nm/mT when the magnetic field is perpendicular or parallel to the light propagation direction, respectively. Theoretical analysis shows that reducing the waist diameter can further improve the sensitivity of the sensor. The proposed sensor is expected to be applied to weak magnetic field measurements in the aviation, vehicle detection and biomedical fields.

提出了一种基于结构调制超长周期微纤维光栅（SULPMG）的高灵敏度光纤双向弱磁场传感器。SULPMG是通过电弧放电和火焰加热拉丝法制造的，传感器是通过将SULPMG与铁芯偏移部分层叠而制成的。通过调节施加的磁场的方向，可以相应地调节磁性流体（MF）的折射率。测量并分析了所提出的传感器的透射光谱响应。对于0 mT至7 mT的弱磁场强度，当磁场垂直或平行于光传播方向时，获得的磁场灵敏度分别为-1.759 nm / mT和1.082 nm / mT。理论分析表明，减小腰部直径可以进一步提高传感器的灵敏度。拟议中的传感器有望应用于航空，车辆检测和生物医学领域的弱磁场测量。