Research On Fiber Demodulation System Of Marine FBG Sensor

The marine economy is an important part of the comprehensive competitiveness of the national economy.The exploitation of marine resources is of great significance to the development of the marine economy.The comprehensive and multi-dimensional information support can greatly improve the mining efficiency of marine resources and the safety of operators.Technologies such as satellite telemetry can only detect the basic information of the ocean surface,and the complex changes of the seabed need to rely on the integrated use of various underwater sensors.The traditional physics sensor is limited by the use environment and structural cost,and can not meet the needs of current applications.The fiber sensor has the advantages of corrosion resistance and electromagnetic interference resistance,so that it can adapt to the harsh environment of the sea.However,there are still many difficulties in the practical application of fiber-optic sensors.The most influential one is the accurate demodulation of the wavelength of light.Therefore,this thesis studies the demodulation system of Fiber Bragg Grating(FBG),which can be applied to marine environment monitoring.The fabrication technology of FBG has gradually matured,but the theoretical analysis of the physical mechanism and characteristics of such fiber-optic sensors is relatively small but crucial.Starting from the spectral characteristics of FBG,the coupling model theory analysis and simulation verification show that the grating parameters have a great influence on the amplitude and spectral width of the FBG reflected signal.At the same time,the core parameters are compared and analyzed.The results show that the proper adjustment of the grating parameters can obtain a more suitable narrow-bandwidth reflection spectrum from the FBG sensor,which creates more favorable pre-conditions for wavelength demodulation.The FBG demodulation system is mainly composed of a signal demodulation module and a signal processing module.The core of the signal demodulation module lies in the selection of demodulation technology.Considering the application background of the system,the accuracy requirements and the cost of hardware equipment,the FBG sensor demodulation system based on the tunable Fabry-Perot filter demodulation technology is selected to be combined with the simplified version of the temperature measurement experiment.The environmental parameters of the simulation system are obtained,and the feasibility of measuring the physical quantity of the FBG sensing demodulation system is verified by simulation.The signal processing module of the demodulation system is mainly used for algorithm processing of the collected signals to obtain more accurate spectral peak wavelengths.According to the requirements of marine meteorological parameters and hydrological parameter measurement accuracy,the conventional FBG sensing demodulation system should measure the center wavelength better than the order of 10 pm.The theoretical analysis and simulation experiments verify the sensing characteristics of the FBG demodulation system.The results show that the Levenberg-Marquardt optimal peak finding algorithm and the adaptive Kalman filter improved algorithm cascade method are used to optimize the system under the condition of hardware equipment.The signal processing module effectively improves the demodulation accuracy of the system,and at the same time improves the stability of the system,enables the system to meet the monitoring requirements of the marine environment,and promotes the product development of the FBG sensor to a certain extent.