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Theorical And Experimential Research On Three-component Photoelastic Waveguide Hybrid-integrated Optical Acceleration Seismic Geophone

Posted on:2007-03-31Degree:DoctorType:Dissertation
Country:ChinaCandidate:D L TangFull Text:PDF
GTID:1118360212989329Subject:Physical Electronics
Abstract/Summary:PDF Full Text Request
In order to improve the oil and gas reserves, people used 3-D seismic exploration to find the oil and gas storage in the shallow and thin layers. The multicomponent seismic exploration requires 3-component seismic signals, which are measured by 3-component geophone in an earthquake. 3-component geophone can measure back and forth horizontal motions in two directions. It is a important thing for 3-D seismic exploration to choose a 3-component geophone with suitable parameters, including nature frequency; cross-axis sensitivity; on-axis sensitivity and applicability for field exploration.In this dissertation, the three-component hybrid-integrated optical acceleration seismic geophone based on photoelastic waveguide is introduced for the first time, which contains the photoelastic waveguide technology and 3-component seismic signal detection technology. Compared with other 3-component geophones, this acceleration geophone has broad-band frequency; low cross-axis sensitivity; high on-axis sensitivity. It is also possible to overcome optical alignment ,long-term stable and handing of fiber in package process when optical fiber sensor is minimized and go into mass production.The research work of the dissertation mainly includes four aspects as follows:1 we model the three-component hybrid-integrated optical acceleration seismic geophone by the system consisting of masses; spring and dampers. The differential equation of motion for the system is found. The static characteristic and dynamic characteristic of 3-component hybrid-integrated optical acceleration seismic geophone (such as: frequency response; phase response; step response etc.) are studied, which are bases of the vibration theory for design the three-component hybrid-integrated optical acceleration seismic geophone2 based on the one-dimensional photoelasitcity when one-dimensional stress is applied on LiNbO3 crystal, we derive the 3-dimensional photoelasitcity when 3-dimensional stress is applied on LiNbO3 crystal. Applying the method of coordinate transform, we obtain the relationship between phase change of light and 3- component acceleration applied on LiNbO3 crystal. The relation is the theory base for designing the three-component hybrid-integrated optical acceleration seismic geophone.3 After obtaining the 3-dimensional photoelasitcity of LiNbO3 crystal, we analyse the level of sensitivity to off-axis accelerations which is a very important parameter for3-axis accelerometer. Combining with the mechanical libration theory and photoelasitcity theory, we design the 3-component hybrid-integrated optical acceleration seismic geophone which cross-sensitivity is 0.4 The Mach-Zehnder waveguide interferometer of the three-component hybrid-integrated optical acceleration seismic geophone is researched detailedly. The optimization structure design of the accelerometer is accomplished. Based on the waveguide ray theory, the condition for single-mode waveguide is derived, and design of single-mode strip waveguide is accomplished with effective index method. Combining with the effective index method, FD-BPM and TBC method, the Y-branching waveguide composed of reflected S-bend is researched. The lightwave propagation in Y-branching waveguide is studied and the FD-BPM method employed to simulate. The Mach-Zehnder waveguide interferometer we designed has good splitting ratio and low-loss.5 In order to make a good Mach-Zehnder waveguide interferometer, Lots of theoretical and experimental researches on process craft of waveguide interferometer have been done. A feasible process flow is made and valuable technological parameters are obtained. The Mach-Zehnder waveguide interferometer is fabricated successfully and the optical measurement is executed.
Keywords/Search Tags:three-component, accelerometer, photoelasitcity effect, waveguide, Mach-Zehnder interferometer
PDF Full Text Request
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