Development Of FBG Demodulation System Based On Laser Scanning And Its Performance Test

In the transportation industry,vibration monitoring of bridges,high-speed trains,rails and other structures is an important research topic and an important part of traffic safety guarantee.The choice of sensors directly determines the ability and effect of physical quantity detection.Since the invention of fiber Bragg gratings in 1978,Fiber Bragg Grating(FBG)sensors have become important research objects in the field of sensor detection,and have been widely applied during the continuous development of technology.Today,FBG sensors have many advantages that traditional sensors do not have when applied to many physical quantities such as deformation,so FBG sensors may have better application prospects.At the same time,in actual engineering,the use of accurate,stable,fast,reliable and low-cost FBG demodulation system is an important prerequisite to ensure good application.This paper analyzes and develops a demodula-tion system based on the scanning of tunable laser,and validates the good results of the demodulation system in the performance test.This paper firstly explains the basic principles of fiber Bragg grating sensors and their vibration detection principles,and it studies and compares several important and common fiber Bragg grating demodulation schemes.The key technologies such as wavelength peak calculation and multiplexing technology in the application of fiber Bragg gratings were studied and analyzed in this paper,and the basic technical scheme was determined.Subsequently,this paper designs a fiber Bragg grating demodulation system based on the method of tunable laser’s scanning,and introduces the design process of the system in two aspects of hardware and software in detail.This paper makes a detailed analysis and calculation of important laser driving circuits and temperature control cir-cuits based on PID adjustment.A feedback analysis method is put forward when ana-lyzing and designing the current source to ensure the stability of the circuit systems.In the aspect of software,the underlying design architecture of "FPGA+Nios Ⅱ" is used.The development tools of Verilog and C language are used,and the driver of each func-tional module,the calibration program of tunable laser and the wavelength calculation program are designed in the software section.The design and application of the host computer program were carried out using the tools of Labview,and the basic functions such as communication and display were successfully completedFinally,a simple test of the system is performed to verify that the demodulation scheme has a good application performance.The demodulation system has a demodu-lation range of 1528nm to 1568nm and a demodulation speed of IkHz.The error be-tween the demodulation system and SM125 is about 5pm,and the detection effect is ideal.In the end of this paper,the system is applied to vibration detection,and the de-tection effect is good.Therefore,through the design and research in this paper,it can be basically determined that the fiber Bragg grating sensing demodulation system can be better applied in practice,and the project cost is greatly reduced.