Research On High Resolution Fiber Bragg Grating Sensing System Based On Photon Detection Technology

Fiber Bragg Grating(FBG)sensors’ features are small,strong anti-electromagnetic interference ability,high reusability,and have been widely used in many fields such as infrastructure construction and aerospace.The key to FBG sensing technology is to demodulate the center wavelength of FBG efficiently.Although existing demodulation methods can achieve it,weak signals are often involved in practical engineering.In the traditional demodulation system,the sensitivity and wavelength resolution of the system are limited by the detector’s own jitter and response time,which makes it difficult to improve its measurement accuracy and detection sensitivity.Therefore,designing a demodulation system with good sensing performance and low price,suitable for weak signal detection,is of great value to promote the improvement of FBG sensing performance.Researchers have found that the application of quantum properties to the field of sensing can achieve high-precision measurements.Therefore,quantum sensing technology has caught widespread concern in recent years.This paper proposed a fiber grating sensing system based on photon detection technology and the corresponding demodulation method,then research on high wavelength resolution FBG sensing system based on photon detection technology.The main content included the following four parts:1.We introduced the relevant basic theory and demodulation methods of fiber grating sensing,analyzed and compared the existing traditional demodulation systems and their principle.Then,we introduced the advantages of fiber grating sensing based on photon detection technology and the devices used introduced.2.In this thesis,we proposed photon counting Fiber Bragg Grating(PC-FBG)sensing system,and introduced the composition and demodulation principle of the system.More,we used Monte Carlo simulation method to establish a simulation model,then we analyzed the influences of light source jitter and FBG sensor’s own jitter.The simulation results showed that the PC-FBG sensor system was more sensitive to the jitter of the light source and the jitter of the FBG sensor itself.If the system has smaller external jitter,the sensing parameters of the system will be better.3.Based on the analysis of the single-wavelength PC-FBG sensing system,we proposed a dual-wavelength PC-FBG sensing system,and introduced its composition and demodulation principles.We compared the sensing parameters of the FBG sensing system using traditional photodetectors such as APD or PIN and the FBG sensing system using single photon detectors through MATLAB simulation.The simulation results showed that the incident power in the single photon detector was 0.5n W,it can distinguish the wavelength drift of 0.01 pm.When the incident power of the APD or PIN photodetectors was 0.001 W,it can distinguish the wavelength drift of 0.1pm at most.Therefore,the PC-FBG sensing system is more suitable for measuring weak signals.4.We did experiments to verify the PC-FBG sensor system,and analyzed the sensor parameters such as volatility,wavelength resolution and wavelength detection accuracy of the single-wavelength PC-FBG sensor system through experiments.Then,we used the Kalman filter algorithm to reduce the counting fluctuation of the system and improve the sensing parameters of the system.Experimental results showed that the wavelength resolution of the single-wavelength-single-pulse PC-FBG sensing system can reach 0.14 pm after using the Kalman filter algorithm for denoising;when the temperature change was 2℃,the wavelength resolution of the single-wavelength-dual-pulse PC-FBG sensing system can reach 0.013 pm,and when the temperature change was 0.1℃,the wavelength resolution was 0.05 pm.