Improving the sensitivity of magnetic field sensing system based on fiber mode-lock laser

• Published in: Optical fiber technology 2025-01, Vol.89, p.104049, Article 104049
• Main Authors: Xu, Jian, Yang, Sa, Ning, Tigang, Yue, Hongwei, Chen, Yan, Zhou, Renlong, Liao, Tao
• Format: Article
• Language: English
• Subjects: Fiber laser; Magnetic field sensor; Mode-locked laser
• ISSN: 1068-5200
• DOI: 10.1016/j.yofte.2024.104049

•A useful technology has been proposed to enhance the sensitivity of fiber laser sensing systems.•The generation mechanism of beat frequency in mode-locked lasers has been analyzed.•An optical magnetometer based on this proposed technology has been experimentally demonstrated. This paper proposed and experimentally demonstrated a useful technology to improve the sensitivity of magnetic field sensing system based on the beat frequency demodulation of fiber laser. The sensing principle of the proposed system is detecting the beat frequency variation which is caused by the length change of laser cavity. A 3D-printed transducer was used in this paper to convert the magnetic field change to the beat frequency variation, which is the essential sensing part as well. Besides, we found that, mode locking technology could conduce to advance the signal-to-noise ratio of the beat frequency signal, which could further significantly improve the sensing sensitivity and frequency resolution. Experiment results demonstrate that the magnetic field sensitivity is −3.52 kHz/mT, and the actual resolution of the mode-locked laser sensing system is one hundred times higher than it in continuous-wave laser.