| With the progress of optical fibre technology,fiber optic sensor has been widely studied and applied due to its excellent performance.Our research direction is the optical fiber sensor.We discussed the detection performance and the influencing factors of optical fiber sensor from the angle of the external environment change detection and material identification.In this experiment,the AAO?anodic aluminum oxide?Bragg film based optical fiber refractive index sensor for the external environment change detection and the micro-nano optical fiber sensor?silica microstructure?for material identification were developed.In this paper,we characterized and anlysesd the property of the two kinds of optical fiber sensors,and then discussed the influence factors of the actual detection and the way to improve the detection sensitivity.Optical fiber refractive index measurement can realize long-distance real-time monitoring,used for environmental testing;and absorption spectra as a physical feature maps,can be applied to the material identification,medical testing,etc.Therefore,the research of the two kinds of optical fiber sensors has important significance for the future.The main contents of this paper are as follows:1.A refractive index sensor based on the AAO Bragg film?1?According to the reflection principle of Bragg grating,we preprared the optical fiber refractive index sensor based on AAO Bragg film.And the sensing characteristics of this device are studied from two aspects:theoretical analysis and experimental detection.Compared with the traditional FBG constructure,the device has the advantages of simple preparation with low cost and high sensitivity,besides,it is also possible to adjust the working range?Reflection center wavelength range?by changing the preparation procedure of AAO film according to the actual demand.?2?Based on the relationship between the sensitivity of the sensor and the porosity of AAO film,we could improve the refractive index detection sensitivity of the refractive index sensor by using phosphoric acid etching method to increase the porosity of AAO thin films.Moreover,the sensitivity achieved 458.3nm/RIU when the refractive index were the range of 1.333-1.376 RIU.2.Absorption spectroscopy detection by micro-nano fiber.?1?In this paper,single-mode fibers were successfully fabricated into a series of micro-nano fibers with different diameters by Hydrogen flame heating assisted Stretching method.The devices of fiber absorption detection were prepared by fixing the micro-nano fiber to PDMS substrate,and the detection limit of R6G solution could achieve to 10-10M.?2?The R6G absorbance changing with the diameter changing of micro-nano optical fibers were discussed from the aspects of experiment and simulation.It was found that the absorbance does not increase with the increase of the evanescent field,but first increased and then decreased with the diameter of these micro-nano optical fibers increased.there exist a maximum value which was conformed with surface adsorption type evanescent field absorption.It is shown that the detected absorption spectrum performance of micro-nano fibers is determined by the surface adsorption and evanescent field distribution.?3?The method of drawing the waist area length extended micro-nano optical fiber is studied,and the waist area length of micro-nanometer fiber was successfully increased to 3 times.The viewpoint of increasing the absorption detection optical path length,the detection result were increased to 3 times compared to the original mciro-nanofiber,and the concentration detection limit of R6G was reduced from 10-10M to 10-1111 M. |
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