Studies On Wavelength Swept Light Source In Fiber Bragg Grating Sensing Interrogation System

Fiber Bragg Grating(FBG)sensing has important applications in transportation,energy security,structural engineering and other fields.The FBG sensing interrogation system based on wavelength swept light source has been widely studied with its advantages such as high signal-to-noise ratio and high interrogation rate.This paper researches on a wavelength swept light source based on a recirculating frequency shifter and the FBG sensing interrogation system based on this wavelength swept light source.The wavelength swept light source based on recirculating frequency shifter has fast swept rate,high swept linearity,and the swept step is precisely controlled.When using it for FBG sensing interrogation,the interrogation rate,the interrogation linearity and the interrogation accuracy can be improved.The main contents are as following:1.The wavelength swept light source based on recirculating frequency shifter is theoretically studied.The principle of high-speed and high-accuracy recirculating frequency sweeping of optical signals by radio frequency signals is analyzed.The principle of FBG sensing interrogation system based on wavelength swept light source is studied.The relationship between the parameters of wavelength swept light source and the FBG sensing interrogation results are analyzed.2.Experimentally studied the output characteristics of wavelength swept light source based on recirculating frequency shifter.By changing the frequency of the radio frequency signal,different swept ranges with spectral flatness better than±1.5 d B are achieved.The swept linearity is 0.99995.Swept step can be adjusted from 10 MHz to20 GHz.The relationship between the parameters of wavelength swept light source and the FBG sensing interrogation results is studied experimentally.The temperature interrogation linearity and static stress interrogation linearity is 0.99718 and 0.99946,respectively.The dynamic stress interrogation sensitivity is 0.012??/Hz^1/2.3.Multi-wavelength swept light source based on recirculating frequency shifter is theoretically and experimentally studied.Multi-wavelength seed light parallel frequency swept technology is used to achieve the extension of the swept range at the same swept step and the same swept rate.The relationship between the swept step,swept range and swept rate are analyzed.Three-wavelength parallel frequency swept output when the swept step is 10 GHz and 5 GHz,the swept linearity is 0.99991,the swept range is 2 nm,and the maximum swept rate is 537 kHz.Based on the multi-wavelength swept light source and multiple FBG sensors to realize the simultaneous sensing interrogation of temperature and dynamic stress.