Multilongitudinal mode fiber laser for highly-sensitive magnetic field measurement

In this paper, a magnetic field sensor based on a multilongitudinal mode fiber laser has been proposed by employing a rotary apparatus modulated by an external magnetic field. Due to the remarkable birefringence change caused by the fiber twist, the polarimetric mode beat frequency (PMBF) of the laser is sensitive to the applied magnetic field intensity. Experimental results show that the PMBF linearly shifts with the variation of the magnetic field intensity and the sensitivity reaches up to 10.4 KHz Oe⁻¹ in the range of 0–270 Oe. Moreover, such a device has the advantages of easy fabrication, low cost and high resolution, offering potentials in the weak magnetic field applications. (paper)