Magnetic Field Sensor Based on Corroded Multi-mode Fiber Structure

Magnetic field detection plays a vital role in various applications, including measuring the strength of the Earth's magnetic field, detecting magnetic anomalies with different characteristics, and military applications such as submarine detection. This paper demonstrates an optical structure which utilizes the single and multimode fiber with magnetic fluid to detect magnetic field. To enhance its sensitivity in detecting magnetic field strength, the multimode fiber (SMS) structure is corroded with hydrochloric acid (HCl). Within the SMS sensor, a short segment of multimode fiber as the sensing element, leading to the occurrence of multimode interference along the fiber. The sensor successfully detects magnetic field strengths ranging from 1.5 to 7.4 mT. The achieved sensitivities for magnetic field strength are −795.2 pm/mT and −327.9 pm/mT, corresponding to the length of MMF at 39 and 45 mm, respectively. The linear fitting coefficients R2 achieved for the 39 and 45 mm MMF lengths are 0.8884 and 0.9814, respectively.