High Stability Fiber Optic Magnetic Field Sensor with Enhanced Linear Range Using Magnetic Feedback Nulling.

This patent application discloses a fiber optic interferometer-type magnetic field sensor which uses an automatic feedback system to limit the range of the magnetic field experienced by the sensor element. A high frequency bias field is mixed with the external magnetic field to be measured and the resulting interferometer output signal is converted to an electric output signal. The electric output signal is mixed with a reference signal having the same frequency as the bias signal to form a baseband negative feedback signal which is converted to a magnetic field and mixed with the bias and external fields to provide automatic feedback.