Vibration Acceleration Detection Technology Based On Mach-zehnder Interferometer

Petroleum, an important strategic resource, is the basis and safeguards of national economy, social progress, even the country itself. In order to make the petroleum supplies meet the requirements of economic construction, it is important to hunt for high reserves and high-quality new oilfields in the petroleum exploration industry. Seismic prospect method is to survey the geological structures underground or explore the oil fields. Seismic geophone, as the first process in the seismic prospect, decides the quality of the oil fields exploration.Taking the advantages of integrated optical waveguide device into account, such as high sensitivity, high accuracy, high integration and anti-electro magnetic interference, an integrated optical waveguide acceleration seismic geophone is designed based on Mach-Zehnder (M-Z) interference structure. Firstly, it is utilized the optical waveguide mode theory to design the single-mode structure of lithium niobate ridge waveguide, which accomplishes the structure design of double M-Z interferometer and simulation of the optical field transmission and mode field distribution by FD-BPM; Then, based on the photoelastic effect of lithium niobate crystals, theoretical analysis of the changes of the optical waveguide refractive index and the mode field distribution under stress by acceleration effected, and simulation of the optical waveguide fundamental mode field distribution by different acceleration effected are well established; In addition to mechanics of materials and mechanical vibration principle, the stress on the integrated optical waveguide sensor unit is analyzed, the phase detection sensitivity is calculated as 0.0896rad/(m?s-2), and the working frequency range is 0~1.389×104Hz; Also, it uses the Micro-fabrication technology to fabricate the ridge waveguide in X cut Y propagation lithium niobate substrate by proton exchange technology, and analyzed the etch mechanism in X cut lithium niobate substrate; A dual sensing arm optical fiber M-Z interference structure and sensing probe structure based upon optical fiber of the light and mechanics of materials is designed, and also it calculated the mass of sensing probe is 445g, the elastic cylinder diameter is 27mm, the height is 30mm, the system sensitivity is 366.9rad/g, and the working frequency range is 0~340.7Hz; According to the theoretical design structure, it uses the sensing probe made by the silicone rubber and iron block to complete the all-fiber optical dual sensing arm M-Z interferometer, and measured the arm length difference is about 6.87mm, and the interfere visibility is about 95.8%; It is to build the experimental system and detect different frequencies and different amplitudes of the acceleration vibration signal, these illustrates that there is an output consistent with the theoretical analysis when the vibration frequency between 50~400Hz, whereas there is a significant distortion output beyond 400~6000Hz, so the sensor can not work in this frequency range. At last, it concludes all the research and looks forward the future work.