Abstract: A novel fiber optic F-P electromagnetic sensor is developed based on magnetic fluid as the medium in F-P interference cavity. A signal demodulation method based on fiber Bragg grating wavelength scanning is proposed. Theory and principle of electromagnetic-controlled refractive index of the magnetic fluid is described as well as the structure of the sensor system. Preliminary experiments are carried out

and the results indicate that there is a fairly good linearity of the measurement characteristic

and the thickness of magnetic fluid film and environmental temperature will affect the measurement results.