Highly sensitive magnetic field sensor based on mode coupling effect in microstructured optical fibers

Abstract

A highly sensitive magnetic field sensor based on mode coupling effect in a microstructured optical fiber (MOF) was theoretically investigated by using the finite element method. Magnetic fluid with refractive index higher than silica was designed to be filled into one cladding air hole in MOF to form a defect core. The coupling wavelength between fiber core modes and defect core modes can be modulated by external magnetic field. Simulation results show that the measuring sensitivity of magnetic field and figure of merit reached 1620 pm/Oe, 0.081/Oe in x-polarized mode and 1790 pm/Oe, 0.045/Oe in y-polarized mode, respectively. Meanwhile, the intensity of magnetic field depicts a good linear relationship with the coupling wavelength for both orthogonal polarized directions in the range of 25–175.9 Oe. The performance of the designed magnetic field sensor can be improved by optimizing the structural parameters in MOF.