Beat frequency dependence of the sensitivity for Faraday-rotation based heterodyning fiber laser magnetic field sensor

The beat frequency dependence of the sensitivity for a Faraday-rotation based heterodyning fiber laser magnetic field sensor is studied, which shows that lower beat frequency results in higher sensitivity. By lowering the beat frequency to 2 MHz, the maximum sensitivity of about 43 Hz/μT to magnetic field has been achieved for a heterodyning fiber laser inscribed on an Erbium doped fiber. It also shows that the beat frequency is dependent on the polarization of the 980 nm pump. Therefore, dynamical tuning of the sensitivity optically has also been demonstrated by tuning the polarization of the 980 nm pump.