Magnetic Field Sensing System Based on 1550 nm Ring Fiber Laser.

Optical fiber magnetic field sensor plays an important role in fiber sensing field. This paper proposed a magnetic field sensing system based on ring cavity fiber laser with the demodulation of beat frequency. The active fiber of the laser was rolled on a Terfenol-D based transducer and act as the magnetic field sensing component. As a kind magnetostrictive material, the length expansion of Terfenol-D rod occurs when a certain magnetic field was applied on it, ultimately lead to the length change of fiber cavity. Thus, a remarkable beat frequency shift can be observed, and the corresponding magnetic field can be measured as well. The proposed sensing system is found to be characterized with simplicity, easy setup, and high resolution. The experiment result shows a sensitivity of 0.33KHz/mT reached.