The Error Analysis And Instrumented Research Of Fiber Bragg Grating Wavelength Demodulation System Based On Tunable Laser

Fiber Bragg Grating as a new type of passive sensors,has been widely used in the industries such as fire early warning of petrochemical and health monitoring of engineering structures due to its advantages of being small size,lightweight,immunity to electromagnetic interference,corrosiveness resistance,wavelength-encoded and easy to build network of sensors.At present,the use of tunable lasers for spectral acquisition and spectral analysis is an important technique in the system of FBG wavelength demodulation.The system of FBG wavelength demodulation based on tunable laser can effectively meet the requirements of demodulation accuracy and demodulation stability in the high-speed FBG system.This paper is aimed at the design and development of high-speed and high-precision FBG wavelength demodulation system,so that the system of FBG wavelength demodulation which is based on tunable laser is studied deeply.This dissertation introduces the structure and principle of the system of FBG wavelength demodulation based on tunable laser at first.The algorithm of peak search and the wavelength correction are elaborated and verified.The design of hardware and software is completed in the in the process of instrumented research of demodulation system.The law of wavelength demodulation error is found in the experiment,the cause of error is analyzed,and the compensation method is proposed.The main contents are as follows:1.In order to improve the accuracy of FBG wavelength demodulation,the corresponding wavelength correction algorithm is proposed.The algorithm of peak search and the wavelength correction is selected for the high-speed FBG wavelength demodulation system,by the experimental verification and analysis.2.Scanning frequency is one of the most important parameters in laser modulation,and it effects on the FBG wavelength demodulation system is studied.This paper finds that the error of wavelength demodulation varies with the scanning frequency,and theoretical analysis is carried out.The wavelength demodulation error is compensated in real time,and the effect of error compensation is verified by experiments.3.In order to meet the engineering application of this system,instrumentation of FBG wavelength demodulation system based on tunable laser is studied.The system and processing software are designed by the thoughts of modularization,and the prototype of the system is built.The HMI and the algorithm of acquisition and demodulation based on C#is realized.At the same time,the system prototype has been tested for long-term performance.The results show that at the scanning frequency of 1KHz,the demodulation frequency of FBG wavelength demodulation system based on tunable laser is 499.23Hz,and the max demodulation error is limited to 1.38pm.It can effectively meet the requirements of high speed FBG system for the accuracy and stability of demodulation wavelength,and the instrumented research of FBG wavelength demodulation system also makes it widely used in various engineering fields.