Optimization And Scheme Design In Engineering Application Of Photonic Optical Fiber Sensing Structure

For the large civil engineering structures such as bridges, tunnels, and dams etc, with large investment, long term of service, adverse circumstances, the security of the structure has been given increasing attention. The important parameter of structural mechanics characteristics and material properties is reflected by stress and strain. Adopting optical fiber sensing technique to measure strain has been an important method for engineers. Compared with the traditional sensors of the electric test such as resistance gage, optical fiber sensor has the advantages of stability, corrosion-resistant, electromagnetic interference confrontation, small volume, light weight, high sensitivity and distribution measuring. With its unique and exceptional nature, Fiber Bragg Grating, widely used in optical fiber sensors, is welcomed to structural health monitoring. However, Fiber Bragg Grating is sensitive to strain and temperature, so there are intersection sensitive problem with strain and temperature for Fiber Bragg Grating Sensor using fiber bragg grating as the sensing element. Photonic crystal fiber itself is not sensitive to the temperature, eliminating the intersection sensitive, and the sensitivity of sensing element can be adjusted by the structure of the photonic crystal fiber.In this dissertation, photonic optical fiber (PCF) especially the sensing PCF subjected to transverse stress,was deeply studied by the finite element method. The main contents are presented as follows:1. The development and research of optical fiber sensor at home and abroad were reviewed. The study of PCF at present and the application in the field of sensor were described. The basic structure, classification and the working mechanism and application of optical fiber were introduced.2. Take total internal reflection photonic optical fiber for example, the sensing structural model subjected to transverse stress was established. Using the finite element analysis software, PCF with different structure parameters was simulated. PCF lateral deformation, affected by the air-hole layer, air-hole diameter, air-hole pitch and fill factor, was discussed respectively. PCF structure was optimized and designed. The reasonable value range of PCF sensing structure was optimized:the optimum value range of fill factor f is 0.6-0.8; the optimum value range of air-hole pitch A is 6μm- 9μm; the optimum value range of air hole N is 5-10. The photonic crystal fiber sensor using PCF as sensing element, according to its use, preparation technology and the cost, chooses the appropriate structure parameter value.3. Combinated to the experience of fiber bragg grating strain sensor in engineering practices, choosing metal tube packing way, using the internal embed installation method, a scheme of photonic crystal fiber bragg grating strain sensor to monitor reinforced concrete simple supported beam was designed. The way that photonic crystal fiber bragg grating sensor was used in the experiment of project was explored. The research presents a reference for engineering application in the future.