| People have not given up on the development and utilization of marine resources ever since ancient times.The rise of communication technology has once again brought a new look to the era.Underwater optical communication is a new type of communication combining the two together that has gradually emerged in recent years.The attenuation of seawater on different wavelengths of light is different.The complexity of inner seawater,the disturbance of seawater,and the variation of temperature will have a great impact on light waves.Studies by scholars have found that seawater has a less attenuation of light in the 450nm?550nm band than in other wavelengths.Because this kind of section belongs to the blue-green band,that is to say,Underwater optical communication is also called blue-green communication.When the light beam travels in water,it will deviate from the direction of propagation to produce expansion of both time and space.The quality of water will also matter.The most obvious change is that the transmission distance of light is limited and the light energy is greatly attenuated.Improving communication efficiency,reducing energy loss,and reducing bit error rate during signal transmission are problems that needed to be solved in underwater optical communication technology.In this paper,the changes of optical signals in the water are studied from two aspects of simulation and experiment.We introduce three theoretical calculation methods for light transmission in water,Small angle approximation,Experimental research and Monte Carlo method are introduced.The randomness and applicability of the Monte Carlo method are verified.The Monte Carlo method is used to simulate the mathematical model of photon motion in the water,and the specific simulation process of photon motion is given.The Rayleigh scattering and Mie scattering models are established and the correlation theory and scattering phase function are analyzed.Rayleigh scattering occurs when a light beam is transmitted in a small molecule,and Mie scattering occurs when it is transmitted in a macromolecule or insoluble particles.In order to be more closer to the actual situation,this paper adopts the theory of Mie scattering transmission.Combining the Mie theory with the Monte Carlo method,using the method of controlling variables,the effects of different water quality parameters such as the beam propagation distance,the radius of the receiving surface,and the attenuation coefficient and asymmetry factor of the seawater on the underwater beam transmission are simulOated.The simulation calculation is carried out by Matlab software,The distribution image of the light pulse on the receiving surface and the variation of the light pulse energy with different parameters are given.By building a blue-green optical communication experimental platform,using LED as the light source,in which the wavelengths are of 500nm?510nm,simulate seawater environment by adding different impurities to the water.Testing the value of the luminous flux of beam,which passes through different impurity environments,thereby analyzing the attenuation of the beam.The experimental data and experimental results are ideal.The research content of this paper has certain reference significance for the construction of the actual communication platform. |
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