Research On The Phase Demodulation Based On Optical Fiber Vibration Sensing Technology And Hardware Implementation

Traditional electrical vibration sensors are susceptible to electromagnetic interference and are extremely limited in use in extreme environments such as the ocean.Fiber optic has outstanding advantages such as small size,light weight,and intrinsic passive safety.As a medium,fiber optic accelerometers,fiber optic hydrophones and fiber optic gyroscopes have been rapidly developed.Among them,fiber-optic vibration sensors are being studied in depth as a new generation of vibration sensing systems and are expected to play an irreplaceable role in the fields of geological disaster warning and monitoring of hydrophone sensors.As the core part of signal processing of optical fiber vibration sensing technology,the research and implementation of phase demodulation technology is particularly important.The main content of this paper is to deeply study the phase demodulation method and the hardware circuit implementation of optical fiber vibration sensing technology.Firstly,this paper analyzes the fundamental principle of fiber interference and the mechanism of fiber phase modulation,and focuses on the effect of stress-strain effect of fiber and temperature-strain effect on the phase of the output light wave.From the analysis of the superposition principle of optical wave field,the formation conditions of interference light are obtained,which establishes the theoretical basis for fiber-optic interferometric vibration sensing.Then,the implementation scheme of the lowfrequency vibration detector and the overall optical path design unit in the fiber-optic vibration sensing system was analyzed,highlighting the important position of the phase demodulation part in the system.Then,the implementation scheme of the lowfrequency vibration detector and the overall optical path design unit in the fiber-optic vibration sensing system is analyzed,The important position of the phase demodulation part in the system is emphasized.Secondly,based on the theory of fiber-optic interferometry,this paper focuses on the in-depth study of optical wave phase demodulation technology.By analyzing the optical wave tuning principle of distributed feedback semiconductor lasers,the internal modulation technology scheme for fiber-optic interferometric vibration sensing is determined.At the same time,this dissertation deeply studies the interferometric phase demodulation technology,and compares the passive homodyne demodulation technology and the phase-generated carrier demodulation technology.The phase generation carrier demodulation technology is theoretically calculated by using the method of Bessel function to provide theoretical basis for the realization of the system phase demodulation.Again,based on the in-depth analysis and research of the phase demodulation algorithm,this paper uses MATLAB to perform simulation analysis to determine the values of the main parameters in the demodulation algorithm,and analyzes the parameters such as modulation frequency,filter cutoff frequency,and signal amplitude.The relationship provides the basis for determining the key parameters of the demodulation module;In demodulation in the process of implementation,in order to solve the disadvantages of low frequency vibration signal real-time performance is not high,based on the LabVIEW programming of demodulation algorithm implementation,innovative use of "producer/consumer" program structure pattern,solve the signal sampling and the contradiction between large amount of data real-time processing,realize the real-time dynamic demodulation of low-frequency vibration signals.Finally,on the basis of the simulation and theoretical research of phase demodulation technology,this paper proposes a scheme for phase demodulation using analog circuits,effectively avoiding the disadvantages of low real-time digital demodulation,and innovatively proposes the removal of intra-modulation amplitude modulation.The method of influence and circuit optimization and improvement for low frequency vibration signal demodulation.Through demodulation of the analog demodulation circuit and the optical fiber vibration sensing system,demodulation of the 0.5 Hz-10 Hz vibration signal is achieved,and the demodulation output linear correlation coefficient is 0.9994.This paper demonstrates the feasibility of analog circuits for low-frequency phase demodulation,and the use of analog circuits to improve the real-time signal processing.At the same time,digital signal processing method which can effectively avoid the impact of environmental factors on the demodulation process,so the hardware-software combination using the methods can effectively play their respective advantages,will implement the low-frequency vibration signals of high precision phase demodulation,provides the direction for further system optimization work.