The Study Of Fiber Grating Demodulation System Based On FPGA

Since the1960s,with the development of optical communication technology andthe continuous development of fiber optic technology,optical fiber sensing technologygradually attracted people’s attention, and become an important research direction of thesensing field. Fiber Bragg grating (Fiber Bragg Grating FBG) sensor is a new type offiber optic sensors, and it has excellent features which many conventional sensors cannot match, such as fiber grating sensor with electrical insulation, anti-electromagneticinterference, acid and alkali resistance, small size and weight light, high sensitivity. Soit is expected to be wide application in the field of large-scale civil engineeringstructures, aerospace, energy, chemical, power monitoring, petrochemical, and others.Wavelength demodulation is the core of the fiber grating sensor technology, andit is closely related to system sensitivity, accuracy and dynamic.It is one of theimportant research direction of fiber grating sensor field.The thesis mainly analyzes the current domestic and international fiber gratingsensor technology trends, and designed to achieve fiber grating demodulation systembased on FPGA and F-P cavity (Fabry-Perot cavity), which implements the waitingfor the measured signal demodulation such as temperature, stress.This thesis first analyzes the basic principles of fiber grating sensor anddemodulation method, and studied the basic principles of fiber grating demodulationsystem,based on tunable Fabry-Perot (Fabry-Perot FP) filtering. On this basis, theauthor designed a fiber grating demodulation system based on FPGA and F-P cavity.The system consists of the FPGA system control module, tunable the fiber FP cavitydrive module, signal acquisition module and data transmission sent four parts. Finally,the design of tunable fiber FP cavity driving circuit experiments were carried out toverify the correctness of the design; fitting result gives a data acquisition circuit. In thispaper, the work done by the following main points:1. The article analyzes the composition of the fiber grating demodulation systembased on FPGA and F-P cavity and introduced the principles and characteristics of theselection key components in the system, such as: the broadband light source, the F-Pcavity and photodetector.And test the main performance indicators of the device.2. The F-P cavity chosen for the system, on the basis of full understanding of itselectrical characteristics, the author designed a drive control circuit based on FPGA. This control circuit has a low cost, simple structure and easy to implement. This paperpresents the detailed design and specific circuit, code, and so on,and test the controlcircuit. The experiments show that this control circuit can achieve the task of drivingthe scanning F-P cavity.3. The paper also analyzes the principle characteristics of the fiber gratingdemodulation system signal acquisition, and according to the needs of the entiresystem’s acquisition task, the author designed FPGA-based signal acquisition systemfor fiber grating，which mainly include the acquisition circuit, based on the main controlcircuit of the FPGA, the data transmission circuit and software design.