| In this paper,based on the Mach-Zehnder interference principle and the anisotropic distribution of magnetic nanoparticles around the fiber optic,a sensor with a single-mode fiber-D-shaped hollow core fiber-single-mode fiber(D-SHS)fiber structure is designed for optical fiber vector magnetic field sensor.The sensing principle and the fabrication method of the optical fiber vector magnetic field sensor are firstly introduced,and then the measurement results of the vector magnetic field and the influence of the D-SHS fiber structural parameters on the performance of the sensor are analyzed through experiments.The main research contents and innovation are:1.Taking advantage of the optical transmission characteristics of D-shaped hollow-core fiber,a fiber-optic vector magnetic field sensor based on magnetic fluid and D-SHS fiber structure is proposed,which realizes the measurement of magnetic field strength and magnetic field direction.The basic structure and fabrication process of the optical fiber vector magnetic field sensor are expounded,and the related theoretical of the sensing principle of the optical fiber vector magnetic field sensor is analyzed.2.The response of the fiber-optic vector magnetic field sensor to the magnetic field strength and magnetic field direction is experimentally studied,and the measurement of two different fiber-optic structural parameters of the fiber-optic vector magnetic field sensor.Through experimental investigation and data analysis,we can obtain: In the magnetic field range of 32 mT-42 mT and when the magnetic field strength is 38 mT,the D-shaped hollow-core fiber side-polished depth is 7.86 μm for the fiber vector magnetic field sensor.The maximum sensitivity of the sensor is 0.24 nm/mT,and the maximum sensitivity magnetic field direction is about 102 pm/°.The D-shaped hollow-core fiber side-polished depth is 18.49 μm for the fiber vector magnetic field sensor.The maximum sensitivity of the sensor is-0.9 nm/mT,and the maximum sensitivity magnetic field direction is about 0.06743 nm/°.3.The effects of three parameters,such as the concentration of magnetic fluid,the side-polished depth of the D-shaped hollow core fiber and the length of the D-shaped hollow core fiber,on the performance of the fiber vector magnetic field sensor were investigated in detail.The following important conclusions are drawn: As the magnetic fluid is diluted,the side-polished depth of the D-shaped hollow-core fiber increases,and the shift direction of the obtained transmission spectrum gradually changes from red-shift to blue-shift.As the length of the D-shaped hollow-core fiber increases,the transmission spectrum shifts in the same direction,but the sensitivity increases gradually.Finally,the interference of the external temperature on the optical fiber vector magnetic field sensor is investigated.Through experiments,it is known that the sensitivity of the optical fiber vector magnetic field sensor to temperature is 0.06667 nm/℃ and a quasi-solution to eliminate the influence of external temperature is proposed. |
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