Research On Acoustic Detection Technology Of Optical Fiber Underwater Bionic Targets

For a long time,underwater detection is important for the development of marine resources and the protection of China's territorial sea rights and interests.With the continuous development of ocean detection technology,the requirements for sonar detection ability and concealment are higher and higher.Dolphins have excellent echolocation ability,which can adapt to the complex underwater acoustic environment.It can use echolocation to forage,communicate and avoid natural enemies.Studying the working principle of dolphin sonar and using the advantages of dolphin sonar for reference in the design of artificial sonar can greatly improve the concealment of artificial sonar detection.In this thesis,the finite element analysis software COMSOL is used to simulate the dolphin sonar.By studying the directional acoustic emission of dolphin head in time domain and frequency domain,the modulation effect of dolphin Sonar on nondirectional point sound sources of different frequencies is analyzed.At the same time,the characteristics of echoes generated by targets of different materials and thicknesses are simulated in the time domain.Time delay and spectrum analysis of the echo signal are analyzed.Based on the simulation of dolphin sonar,a dolphin head sonar model is established by the equivalent medium method.The dolphin sonar model is used for underwater experiments.The acoustic sensitivity of the fiber grating is ued to build an optical fiber sensing detection system.The dolphin sonar model is used for underwater experiments.The acoustic sensitivity of the fiber grating is used to build an optical fiber sensing detection system.The optical fiber hydrophone is placed in the underwater sound field to receive the echo signal.In this thesis,dolphin sonar is modeled and analyzed,and a dolphin-like sonar model is made for underwater sonar detection experiments.A fiber-optic sensing detection system is built,and a fiber-optic hydrophone is used to detect the bionic detection echo.Aluminum and acrylic columns with a radius of 50 mm and aluminum and acrylic shell targets with internal radii of 20,30 and 40 mm are placed into the underwater sound field respectively.The optical fiber hydrophone is used to collect the transient echo signal and analyze the collected data to realize underwater detection of targets with different materials and thicknesses.