Magnetic field measurement by using a multilongitudinal mode fiber laser

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 in the range of 0–270Oe.