Research On The Improvement Of Phase Demodulation Method Based On Optical Fiber Vibration System

The tsunami triggered by the seabed earthquake is extremely destructive and poses a very serious threat to the safety of life and property.Therefore,it is particularly important to establish a scientific and effective earthquake and tsunami warning system.Marine environment conditions are complex and difficult to supply and maintain traditional sensors.Interferometric optical fiber sensors have been widely studied in the field of earthquake and tsunami warning due to their outstanding advantages such as electromagnetic interference resistance,corrosion resistance,high sensitivity detection,small size and easy integration,and passive probe characteristics.Interferometric optical fiber sensing technology is used as a means to invert the measured vibration signal by measuring the change of the interference signal.Among them,the phase demodulation method of the interference signal is a key problem in the detection process and has a high research value.In this paper,the improvement of the phase demodulation method of optical fiber vibration system is studied,which makes the system more stable and reliable,and achieves the purpose of high-precision vibration signal detection.Firstly,this paper expounds the background meaning of the research topic,introduces the current situation of the optical fiber sensor and the phase demodulation method,and analyzes the cause and phase modulation principle of optical fiber stem in detail.Then,this paper explains the optical circuit structure and optical fiber vibration detector mechanism of the optical fiber vibration system,and focuses on the phase generation carrier technology,which includes modulation and demodulation,modulation is divided into internal modulation and external modulation,demodulation is divided into differential cross multiplication and arctangent demodulation method.According to the shortcomings and limitations of traditional phase generation carrier demodulation technology,such as the results are easily affected by environmental interference,interference signal amplitude,modulation depth;The basic frequency mixing method is limited to small signal detection.Arctangent demodulation is discontinuous.On the basis of the differential cross-multiplication demodulation method in phase generation carrier technology,the structure of the algorithm is innovated,and an improved demodulation method is proposed.The interference signals that filter out DC components and their basic frequency mixing signals are used for frequency multiplier,differential,differential,division,etc.After the calculation,the signals to be measured are obtained,and the principle is deduced and simulated.The feasibility of the signal is verified.On the basis of the Arctangent demodulation method in phase generation carrier technology,the boundary jump of the demodulation signal is analyzed and judged logically,and the phase compensation method is adopted.The simulation comparison before and after proves the necessity of phase compensation.The modulation depth parameters of the three methods of differential cross multiplication demodulation method,arctangent demodulation method and improved phase generation carrier demodulation method are analyzed,and the best value is selected.The accurate parameter setting is demodulation.The prerequisite of the signal to be measured.Finally,the optical fiber vibration test system is set up and the parameters of the experimental devices and equipment are explained.The vibration signals in the frequency range are tested,and the demodulation effect is good,and the linearity response is very good.In this paper,the phase generation carrier demodulation method is innovatively improved and successfully applied to the optical fiber vibration sensor system to realize the detection of vibration signals in low frequency band.The performance indicators are as follows: the average sensitivity can reach 59.53 dB re rad/g;Dynamic range higher than135.4dB;The accuracy of the system is 0.199?g,which can meet the demand of measuring vibration signal.The research in this paper improves the disadvantages of the traditional phase demodulation method,makes the system enhance the anti-interference ability of the environment,improves the accuracy and accuracy of the demodulation,and obtains a higher linearity,and is successfully applied to the interference optical fiber sensing system.Improve the performance indicators of the system,It is of great significance to meet the needs of submarine seismic detection in marine tsunami early warning.