A novel magnetic field sensor consisting of magnetic fluid (MF) and etched highly birefringent fiber loop mirror (Hi-Bi FLM) is proposed in the paper. The sensor is based on the etched FLM interferometer by using the property of the controllable refractive index of MF under external magnetic field. The refractive index of MF is changed by a tunable magnetic field and the resonant dip wavelength produced by the FLM shifts correspondingly. The magnetic field intensity can be measured by detecting wavelength shift. High sensitivity of 11.31pm/Oe and a resolution of 0.1Oe are obtained for the proposed magnetic field sensor.
Chemical etching process for PANDA polarization-maintaining fiber (PMF) in HiBi fiber loop mirror (FLM) is studied detailedly in this paper. The PMF is inserted into the FLM whose etched length is about 3cm. Due to decrease of the fiber diameter, the whole wavelengths of transmission dips shift to the short wavelength because of the reduction of birefringence when the PMF is etched. The result shows that the wavelength spacing between two interference minima increases from 19nm to 22nm when chemical etching ends, the thinned PMF is sensitive to the external environment and can be applied to many biochemistry sensing applications.