Highly-sensitive magnetic field sensor based on fiber ring laser

A highly sensitive magnetic field sensor based on a fiber ring laser has been proposed and experimentally demonstrated. The magnetic field sensor was fabricated by introducing a rotary apparatus modulated by an external magnetic field into the fiber cavity to twist one section of the fiber. Due to the remarkable birefringence change induced into the laser cavity, the beat frequency generated between two polarizations of the laser is sensitive to the variation of applied magnetic field intensity. Experimental results show that the polarization mode beat frequency linearly shifts with the increment of the magnetic field intensity and the sensitivity reaches up to 7.09 KHz/Oe in the range of 0 - 437 Oe. Therefore, it will be a promising candidate for the weak magnetic field applications including military, hazard forecast and biomedical fields.