| Optical fiber sensors have attracted extensive attention with many advantages,such as small size,high sensitivity,anti-electromagnetic interference and easy integration.There are broad application prospects for optical fiber sensors in aerospace,military defense,medical and other fields.Magnetic fields have a great influence on the normal use of precision electronic equipment in these fields,so monitoring the magnetic field environment is particularly important.Based on the research status of optical fiber magnetic field sensor at home and abroad,the few mode fiber(FMF)magnetic field sensor with tapering in different lengths are prepared.The FMF and the magneto refractive effect of magnetic fluid are used for forming the sensors.The magnetic field sensing characteristics have been studied in detail.The main research contents of the thesis are as follows.Firstly,the basic profile of magnetic fluid is introduced.The structural parameters of the FMF are analyzed briefly.The theoretical model is established and the transmission modes of FMF are analyzed.The transmission mechanism of the sensor is analyzed in detail.Secondly,the preparation method of the tapered FMF magnetic field sensor is studied.The operation steps and parameter selection in preparation are introduced.The transmission mechanism of each preparation stage is analyzed and the transmission spectra of the sensors are analyzed.Thirdly,the temperature sensing characteristics of tapered FMF sensor are studied.The sensors with different tapered length are prepared and the transmission spectra of these sensors are analyzed.The temperature characteristics of the sensors in different tapered length are explored.The relationship between different temperature and wavelength shift is analyzed.Finally,the magnetic field sensing characteristics of tapered FMF are studied.The influence of different tapered lengths on the magnetic field sensitivity is explored.The influence of the different access length of FMF on the magnetic field sensitivity isanalyzed.The effects of different magnetic field directions on the magnetic field sensitivity of this type of sensor are analyzed and compared. |
