Research On Signal Coupling And Noise Reduction Of Ocean Bottom Optical Fiber Seismometer

Placing the ocean bottom optical fiber seismometer directly on the seabed for seismic observation is the main method of capturing and identifying submarine seismic waves.The seabed interface is mostly soft sediment and the impact of water flow or the inclination of the ocean bottom seismometer itself will reduce the signal detection effect.The complex background noise of the environment also restricts the detection distance of the ocean bottom optical fiber seismometer.In order to improve the signal detection and recognition ability of the high-sensitivity ocean bottom optical fiber seismometer,this paper deeply explores the method of obtaining high signal-to-noise ratio seismic wave from signal coupling and filtering processing.This paper includes the following three aspects:The research on ocean background noise and sound propagation model.This part firstly makes the research on the noise characteristics and the influencing factors of the noise intensity,which including the ocean microseismic,the ocean wind and waves,the ship sailing and the submarine microseismic.Then studies the mechanism of submarine seismic wave signal generated by ocean wind and wave and ship navigation,deduces the trajectory equation of submarine seismic wave signal,obtains its propagation law.In the end,this part figures out the feasibility of using ocean bottom seismometer to detect long-distance submarine seismic wave and retrieve sound source information.Coupling research and structural design of ocean bottom seismometer cabin.The springmass-damping model of ocean bottom seismometer is established.It is proposed that the ocean bottom seismometer should be designed into a flat shape and buried in the hard sedimentary layer,which helps to improve the signal coupling ability and ensure that the average density of ocean bottom seismometer is equivalent to the average density of environment as far as possible;A cabin of ocean bottom seismometer is designed.The sacrificial anode method is proposed to improve the anti-corrosion ability,and the stress-strain analysis of the cabin is carried out to ensure that there is no yield failure;Modal analysis and harmonic response analysis are carried out to further study the influence of the cabin and sensing module structure of ocean bottom seismometer on vibration signal transmission.Signal simulation and filtering noise reduction of ocean bottom seismometer.According to the convolution model of submarine earthquake,this paper simulates a reasonable submarine seismic wave signal;The ensemble empirical mode decomposition is used for the simulation signal,the optimal noise reduction smooth model is established as the evaluation function,and the optimal algorithm is selected to reorganize the decomposed signal;The optimal algorithm is compared with empirical mode decomposition algorithm and median filter algorithm.The results show that it can effectively improve the signal-to-noise ratio and signal detection ability.At the same time,the noise reduction experiment of land vibration signal is carried out.The P-wave and S-wave waveform can be clearly distinguished after noise reduction,which improves the signal recognition ability;The method of burying ocean bottom seismometer on the bank is used to detect the ground motion data,and the longdistance ground motion signal is denoised to improve the detection distance.