Study On Fabry-Perot Fiber-optic Sensor And Mechanism Of Improving Its Sensitivity

F-P optical fiber sensor is to construct the F-P cavity on the optical fiber to realize the double beam interference.When physical quantity to be measured changes,the optical phase difference would change,causing interference spectr ?m shifts.Sensitivity is one of the most important parameters to characterize the performance of the sensor and most of the current researches focus on pursuing higher sensitivity.Based on the sensing mechanism of F-P sensor,this paper discusses influence factors of sensor sensitivity and seeks methods to improve sensitivity of different physical quantities:Aiming at that the former discuss of the relationship between sensitivity and cavity length is not sufficient,this paper carries out the theoretical analysis of different types of F-P sensor sensing mechanism,discusses relationship between sensitivity and cavity length,makes mathematical model and plots the spectral drift of different cavity length.Further more,the influence of two F-P cascaded on sensitivity is discussed,the mathematical model of different cavity length ratio is discussed and the spectral drift of different cavity length ratio is plotted.Thus,several methods to improve sensitivity are obtained: construct the sensitive cavity reasonably,shorten the length of cavity,and construct the Vernier effect.Aiming at the research status of low sensitivity in h?midity sensor,this paper demonstrates h?midity sensor with agar cavity and air cavity cascaded to realize three-path light interference.The simultaneous use of refractive index and cavity length change information is realized,performance test experiment of the sensor is carried out and a high sensitivity of 2.73 nm/%RH is achieved.On this basis,analysis and improvement of the h?midity sensor is carried out,to solve the problem of third surface crosstalk,by conducting all-agar cavity h?midity sensor.It is the first time to achieve the full use of sensing information.Sensor preparation and performance testing experiments is conducted,and the ultra high sensitivity is tested to be 4.10 nm/%RH.Aiming at the contradiction between the sensitivity and the measurement range of the pressure sensor in current research,based on amplification the Vernier effect offerring on sensitivity,this paper demonstrates pressure sensor of Surlyn cavity and air cavity cascaded with Vernier effect,to realize the measurement range of the sensor would not be reduced due to the pursuit of sensitivity.Sensor preparation and performance testing experiments is conducted,the amplification factor is 7.56,and the sensitivity is tested to be 0.236 nm/kPa.Aiming at research status of material limitation for temperature sensor sensitivity,based on amplification the Vernier effect offerring on sensitivity,this paper demonstrates temperature sensor of SiO2 cavity and air cavity cascaded with Vernier effect,to release sensitivity from the material limitation.Sensor preparation and performance testing experiments is conducted,the amplification factor is 33.8,and the ultra high sensitivity is tested to be 0.483 nm/?.