【作者】 王阳；

【导师】 张鹏；

【作者基本信息】 长春理工大学 ， 光学工程（专业学位）， 2019， 硕士

【摘要】 蓝绿激光水下通信是近年来水下通信的研究热点之一。随着水下传感与机器人、水下激光雷达、水下图像传输、水下光通信等应用的兴起,深入研究激光束在水下的湍流效应及通信性能就显得尤为重要。激光束在水下传输过程中受到散射、吸收的衰减效应,限制了激光束在水下的传输距离,降低了水下激光通信质量,故如何提高水下通信质量降低误码率等相关问题尤为重要。为了降低海洋湍流对水下系统链路性能的影响,本文提出了具有抗大气湍流的性质的处于蓝绿波段的光孤子形脉冲和贝塞尔光束应用于水下传输系统。首先,介绍了海洋吸收、散射、湍流的基础理论,介绍了激光在水下传输的研究方法,包括Born近似法,Rytov近似法、随机相位屏法、小角度分析法、蒙特卡罗法。其次,假定水下通信系统是开关键控OOK调制的情况下,利用激光在水下的传输过程的研究方法结合海洋弱湍流Lognormal模型,首先推导出了光孤子、矩形、高斯光束的水下通信的闪烁系数模型和误码率模型,分析了不同动能耗散率、温度方差耗散率、Kolmogorov微尺度、盐度变化与温度变化诱致的比值、接收孔径时信噪比与误码率的关系、距离与时域展宽的关系,通过与高斯和矩形光束对比,验证了光孤子脉冲用于水下通信的优势,为下一步研究提供理论参考;其次,利用傅里叶变换和随机相位屏的方法仿真了贝塞尔光束经过海洋湍流后的光斑情况,推导出了贝塞尔光束水下通信受湍流扰动的Rytov一阶干扰项,结合Matlab数值模拟了不同海洋参数下的贝塞尔中心亮斑与闪烁系数的关系和通信距离与误码率的关系从而得到了贝塞尔光束中心亮斑直径的大小对闪烁系数的影响和不同湍流系数对误码率的影响。最后,设计了强度调制/直接检测开关键控OOK调制格式的贝塞尔光束、高斯光束的不同信道下的水下通信实验,搭建了清水、湍流、水流、气泡和散射剂信道下速率为1-4MHz的方波信号传输实验和清水、湍流、水流信道的速率为2.406Mbps的二进制数字通信实验,分析了不同信道下的信号波形和峰值抖动和功率与通信误码率的关系,通过与高斯光束对比,验证了贝塞尔水下通信抗湍流和水流的优势。本文研究的内容对未来水下无线光通信领域的实用化等有一定的参考价值。更多还原

【Abstract】 Blue-green laser underwater communication is one of the research hotspots of underwater communication in recent years.With the rise of underwater sensing and robots,underwater laser radar,underwater image transmission,underwater optical communication,etc.,it is particularly important to study the turbulence effect and communication performance of laser beam under water.The attenuation effect of scattering and absorption of the laser beam during underwater transmission limits the transmission distance of the laser beam under water and reduces the quality of underwater laser communication.Therefore,how to improve the quality of underwater communication and reduce the bit error rate is especially important.In order to reduce the influence of ocean turbulence on the performance of underwater system links,this paper proposes an optical soliton-shaped pulse and Bessel beam in the blue-green band with anti-atmospheric turbulence properties applied to the underwater transmission system.Firstly,the basic theory of ocean attenuation,scattering and turbulence is introduced,and the research methods of laser transmission under water are introduced.Secondly,assuming that the underwater communication system is under key-controlled OOK modulation,the underwater communication process of the optical soliton,rectangular and Gaussian beam is first derived by using the research method of laser underwater transmission process combined with the ocean weak turbulent Lognormal model.The flicker coefficient model and the bit error rate model are used to analyze the relationship between different dynamic energy dissipation rate,temperature variance dissipation rate,Kolmogorov micro-scale,ratio of salinity change and temperature change,signal-to-noise ratio and bit error rate at receiving aperture.The relationship between distance and time domain broadening,compared with Gaussian and rectangular beams,verifies the advantages of optical soliton pulses for underwater communication,providing a theoretical reference for further research;secondly,using Fourier transform and random phase screen The method simulates the spot condition of Bessel beam after ocean turbulence,and derives the Rytov first-order interference term of the Bessel beam underwater communication turbulent disturbance.The Matlab numerical simulation of Bessel center brightness under different ocean parameters is simulated by Matlab numerical simulation.The relationship between the spot and the scintillation coefficient and the relationship between the communication distance and the bit error rate,so that the size of the Bessel beam center spot diameter is obtained.Effects of different turbulence coefficients and coefficients of sparkle error rate.Finally,an underwater communication experiment under different channels of Bessel beam and Gaussian beam with intensity modulation/direct detection and key-controlled OOK modulation format is designed,and the rate of clear water,turbulence,water flow,bubble and scattering agent channel is set to 1-4MHz square wave signal transmission experiment and binary digital communication experiment with clear water,turbulent flow and water flow channel rate of 2.406 Mbps,analyzing the relationship between signal waveform and peak jitter and power and communication error rate under different channels,through Gaussian The beam contrast confirms the advantages of Bessel’s underwater communication against turbulence and current.The content of this paper has important theoretical value and guiding significance for solving some computational difficulties and frontier problems in the field of underwater wireless optical communication.更多还原