Study On Sensing Based On Liquid Crystal Filled Fabry Perot Cavity And Photonic Crystal Fiber

Fiber sensors play an important role in scientific research and application fields because of their flexible structural design,changeable optical properties and diverse inclusion.The birefringence characteristic,electric field and temperature response characteristics of liquid crystal are helpful for the application of optical fiber sensors in the field of high precision sensing.The combined liquid crystal fiber sensor usually has the problems of large size and narrow sensing range.Therefore,this paper focuses on the transmission characteristics of liquid crystal fiber sensors,and designs liquid crystal fiber sensors for different use and different environment.The main research contents of this topic include:First,the fiber Fabry-Perot sensor filled with liquid crystal is analyzed by numerical calculation and theoretical simulation,and then the influence of various parameters of liquid crystal resonator is studied,which shows that that the vernier effect can improve the sensitivity.Based on this,a hydraulic sensor with two Fabry-Perot cavity realizes the the water pressure sensing measurement using the vernier effect.When the temperature decreases,the water pressure sensitivity increases from 6.03 nm/k Pa to 12.87 nm/k Pa.A pull sensor based on single Fabry-Perot liquid crystal cavity is proposed and fabricated.The vernier effect is realized by using the ordinary and extraordinary refractive index of the liquid crystal,and then the high sensitivity measurement of the pull sensor is realized.At the same time,the sensing parameters such as different wavelength,cavity length and casing diameter are studied,which have different sensing sensitivity and range.The pull sensing sensitivity is 46.76 nm/N when its casing diameter is 5.8 mm and cavity spacing is 0.16 mm.A temperature sensor based on liquid crystal Fabry-Perot cavity is innovated and manufactured,which greatly reduces the size of the probe to 3.0 mm×0.3 mm×0.3 mm.A Fabry-Perot temperature sensor filled with 5CB liquid crystal has a high temperature sensitivity of 19.55 nm/℃,which has been improved by nearly an order of magnitude.The sensing range of the liquid crystal fiber Fabry-Perot temperature sensor increases from room temperature 24 ℃ to 48 ℃ by changing liquid crystal.The magnetic field sensor based on photonic liquid crystal fiber is studied and fabricated.Firstly,the transmission properties of single end and both ends filled photonic liquid crystal fiber of different type of LCs are studied.Secondly,the modulation effect of electric field intensity and frequency on transmission is studied to verify the influence of LCs molecular arrangement on transmission intensity.Finally,the effect of magnetic field on light intensity of liquid crystal photonic crystal fiber magnetic field sensors and the sensing characteristics of liquid crystal magnetic field sensors are studied.The magnetic field sensitivity is0.445 %/mT,and the magnetic field sensing range is 32-195 mT.