Study Of Fiber Magnetic Field Sensing Based On Magnetic Fluid

Magnetic fluid (MF) is a stable colloidal suspension of nanosized magnetic particles in a carrier liquid. In recent years, MF-based fiber-optic magnetic field sensors have attracted much attention of researchers because of their advantages such as high compactness, anti-corrosion and immunity to electromagnetic interference.A magnetic field sensor based on an etched thin-core fiber modal interferometer (TCFMI) with high sensitivity is studied. At first, the theoretical analysis of sensing principle and the fabrication process of the sensor are presented. Then we analyze the sensing performance of the sensor on magnetic field at around 1550 nm wavelength. And the performances of sensors with different TCF diameters are compared. Temperature response of the sensors are also investigated. Experimental results show that, cross-sensitivity between magnetic field and temperature is an important issue to be solved.Then, a dual-parameter measurement scheme based on an etched TCFMI cascaded with a fiber Bragg grating (FBG) is proposed. The theoretical analysis of sensing principle and the fabrication process of the sensor are presented. And the sensor's responses on magnetic field and temperature are also studied. Experimental results show that, the reflection of the FBG is sensitive to magnetic field and temperature, and the Bragg wavelength is sensitive to temperature. Thus by using the sensing matrix method, the intensity variations of magnetic field and temperature can be measured simultaneously. And the repeatability, reliability and the response time of the sensor are also investigated.