Research On All-fiber Laser Vibration Measurement Technology With Broad And Tunable Frequency

The heterodyne laser vibration measurement method based on optical Doppler Effect has the advantages of high precision and non-contact.However,the traditional heterodyne laser vibration measurement system based on acousto-optic modulator has complicated optical path and the distance between the system and the target must be short.Modulation frequency range of the acousto-optic modulator is limited,and one acousto-optic modulator produces only one fixed modulation frequency.Therefore,this paper researched an all-fiber laser vibration measurement technology with broad and tunable frequency.This technology employs a dual-parallel Mach-Zehnder modulator to generate a carrier-suppressed single-sideband signal which acts as the reference light signal to beat with the probe light signal and facilitates non-contact vibration measurement according to the optical Doppler Effect.This technology has the advantages of high precision,dynamically adjustable measuring range,full-frequency modulation,identifiable vibration direction,simple optical path and etc.Polarization-maintaining fiber is employed to realize long distance measurement and transmission,and the system can be immune to external electromagnetic interference,then the signal-to-noise ratio of the system will be improved.The technology uses the Hilbert Transform to perform time-frequency analysis on the acquired electrical signals,and calculates the vibration state according to the optical Doppler shift frequency formula and velocity integral,and then the random vibration measurement can be realized.The main research work carried out in the following areas:The first chapter expounds the research background and significance of the subject,introduces the research status of laser measurement at home and abroad,and summarizes the main contents of this paper.The second chapter studies the basic principle of laser measurement technology,and analyzes the method of using the double parallel Mach-Zehnder modulator to realize the frequency shift of the reference beam.Then the overall scheme of the laser vibration measurement system is designed.In the third chapter,based on the principle of DC bias voltage control of the Mach-Zehnder modulator,the DC bias voltage control circuit board of the double parallel Mach-Zehnder modulator is designed.The fourth chapter selects and designs the required hardware and software environment to builds the system prototype according to the laser vibration measurement scheme has been designed.The fifth chapter designs the experimental verification program,and uses the Hilbert transform to perform time-frequency analysis on the acquired beat frequency signal to realize the recovery of the vibration signal.The sixth chapter summarizes the full text and puts forward the prospects for the shortcomings in this paper.