Optical Seismic Measurement And Key Technologies Research

The measurement of seismic waves in the national economy is of great significance, bywhich details of the geological structure can be obtained. It can also be applied in mineralexploration, geophysical studies, and early warning of geological activities and disaster.Compared to the traditional electromechanical seismometer, the optical seismometers andstrainmeters has great sensitivity, broad bandwidth, excellent characteristics of low frequencyand also has no attached electronic circuit in the sensing element of fiber seismometers andlarge dynamic range. In addition, with the current optical seismic monitoring technique, it canconsist of a large-scale sensing array.This paper studied the optical seismic monitoring principles and methods, and built theoptical seismic system. Our research are mainly based on the following aspects: Study ofoptical seismic measurement principle, respectively carry out spatial light path structure oflaser interferometer measurement principle and the optical fiber seismic sensor technologyprinciple, Analysis of the noise of optical measuring system.By optimizing the demodulation algorithm of Phase Generated Carrier (PGC), theinfluence of the B value has been eliminated with the involvement of stability onlinemonitoring function. The algorithm is based on the PGC demodulation technique. Throughcomputing the Bessel function of the interference signal, the interference intensity of B valuecould be eliminated, which reduces the dependence of the output signal interference contrastand greatly increases optical seismometer’s anti-jamming capability. In addition,low-frequency monitoring signal is added into the carrier signal of PGC, and achievesreal-time online monitoring of stability without increasing the burden of hardware. Moreover,it provides system state data for signal analysis, reduces the error in the signal analysisprocess, and improves interferometer commissioning and operating efficiency.The paper researches and designs a long baseline strainmeter with integrated opticalstructure. We improved the design to integrate the optical devices of the strainmeter, reducesadjustment devices of optical system of strainmeter and improves the optical system stability.The whole design is based on the original models of long baseline strainmeter. We carried outthe optical system of the laser strainmeter, calibrated the laser strainmeter, and sdudied its noise performance in detail. We designed and built optical vacuum line,and constructed a22m long baseline laser strainmete, and carried out experiments of long baseline laserstrainmeter with piping closed.The paper designs a small-scale high-precision fiber optic seismometer, studies thestructure and sensing principle of it, and carries out the design of the optical path structural.We have designed the fiber optic sensing structure, improved the sensitivity of the highsensitivity of optical fiber, and analyzed seismometer noise source. A device for making thesensing structure of fiber seismometer was designed and built, which help us to constructthe high-precision fiber optic seismometer principle prototype. The test system of fiber opticseismometer was designed and analyzed to achieve a single-dimension vibration signal toload and withstanding of high load experiments.. Through fiber-optic seismometer test system,we carried out the experiment of the fiber seismometers. Experimental analysis show that thesensitivity of fiber optic seismometer is up to9.4rad/nm contrast with the standard quartzaccelerometer.