All-fiber magnetic field sensors based on magnetic fluid-filled photonic crystal fibers.

A method for measurement of a magnetic field by combining photonic crystal fibers (PCFs) and magnetic fluid is presented and experimentally demonstrated. The magnetic fluid is filled into the air holes of the cladding layer in the PCF. Due to the tunable refractive index property of the magnetic fluid, the refractive index difference between the fiber core and cladding layer is changed with the external magnetic field. The magnetic field can be directly detected by measuring the intensity of the transmission light. A series of magnetic fields with different strengths have been measured with the sensor. The experimental results show that a resolution of up to 0.09 Oe is achieved, and a good repetition is demonstrated experimentally. Compared with other expensive methods, the proposed method possesses high sensitivity and low cost.