Research On Noise Suppression Of Fiber-optic Hydrophone Array

The fiber-optic hydrophone has substituted the piezoelectric hydrophone in the ship-borne towed sonar system step by step.But the fiber-optic hydrophone has higher sensitivity,and the flow noise and ship interference noise of the array itself in the towed state severely influence the detection performance of the sonar.Aiming at these two problems,the research of fiber-optic hydrophone array noise suppression has been studied.The main research contents are as follows.(1)The project on fiber optic hydrophone towed array has been researched.Firstly,the main components and related design of the fiber-optic hydrophone towed array are introduced,and then the array design,optical design,acoustic array section design,vibration isolation section design and tail sleeve assembly design are analyzed.(2)The noise suppression technology of towed flow has been researched.Firstly,the mechanism analysis and theoretical model of towed flow noise have been analyzed.Then,based on the mechanism,the suppression of flow noise is studied from four aspects,including the anti-acceleration sensitivity of fiber-optic hydrophone,the front and rear vibration isolation sections,the optimization of array devices and the zero buoyancy of array.And then,the specific analysis methods of flow noise are described.Finally,the effects of different acceleration sensitivity,different size of fiber-optic hydrophone and different front and rear vibration isolation sections on the convective noise are analyzed and verified through the lake test.The test results show that the better the anti-acceleration sensitivity is,the lower the towed flow noise is.When the frequency is above 100 Hz,reducing the diameter of the probe is beneficial to reduce the noise transmission on the surface of the sheath.Increasing the spacing between the two sides of the hydrophone is beneficial to reduce the towed flow noise at the hydrophone.Installing the front and rear vibration isolation sections can significantly reduce the flow noise.And the longer the vibration isolation section is,the better the effect is.Finally,a 32-element fiber-optic hydrophone array is developed,and the lake test proves that the towed flow noise index meets the application requirements.(3)The research on the noise interference cancellation technology of the ship has been researched.The ship noise is the main source of noise jamming in the head and tail direction of the towed array.Firstly,the ANC and IBF methods have been researched.The former has high complexity and high cost in engineering application,and has great limitations.The latter has high sidelobe,which is 6 d B higher than that of the CBF method,and may have negative sidelobe.In this paper,an upgraded IBF algorithm based on MAR model has been put forward,which can reduce the sidelobe and upgrade the implementing of target azimuth detection with the help of array data.Then the simulation results indicate that the resolution ratio of target is upgraded.Finally,the sea trial data of the South China Sea is analyzed,and the IBF algorithm and the upgraded algorithm have been compared.The results reveal that the algorithm in this paper has better noise interference suppression impact on the ship,and the sidelobe is also suppressed,which effectively upgrades the target detection performance of the fiber towed array.