Optical fiber cantilever magnetic field sensing probe based on magnetic polymer microellipsoid

In this paper, a highly sensitive fiber cantilever magnetic field sensing probe based on magnetic polymer microellipsoid is proposed. The preparation process of the fiber sensing probe is simple, and its cost is low. First, a fiber cantilever is fused at the end of the multimode fiber. Then, a magnetic polymer microellipsoid is coated at the end of the fiber cantilever, and a fiber optic Michelson interferometer is obtained. The incident light is reflected and transmitted at the interfaces between the multimode fiber and the air, as well as the interface between the multimode fiber and the fiber cantilever. One part of the incident light is reflected at the interface between multimode optical fiber core and air. Another part of incident light is transmitted and continues to travel forward along the optical fiber cantilever, and is reflected at the interface between fiber cantilever and air. The higher-order modes are excited. The reflected beams interfere with each other inside the multimode fiber to form a michelson interference spectrum. The fiber cantilever sensing probe with the length of 663 μm and the diameter of 37 μm is investigated in detailed. The changes of the center wavelength of the interference peak near 1440 nm with magnetic field intensity varying are recorded, and the magnetic sensitivity of the proposed sensor probe reaches −0.80991 nm/mT. It will has a important application prospect in many fields such as medical diagnosis, motor control system and industrial automation.