Design And Implementation Of Underwater Video Transmission System Based On LED

Since the 21 st century,the development of marine resources has aroused widespread concern all over the world.The increasing in underwater exploration related work has made the demand for underwater communication technology also increase.Compared with land-based communications,radio waves and sound waves underwater communications are greatly restricted by environmental factors.On the contrary,the visible light underwater communication technology overcomes the influence of the complex environment of seawater and can realize high-frequency,large-capacity carrier signal transmission.Based on the above application background,this paper designs a set of LED-based underwater video transmission system,which realizes the short distance transmission of video signals in the water.The main research contents are as follows:(1)The optical channel of the visible light underwater transmission system is analyzed,the absorption and scattering model of the light signal by seawater is established,and the overall loss model of the light signal is obtained when the light signal is transmitted underwater.Through the analysis of the loss model,it is found that the blue and green light in the visible light band are the most suitable light sources for underwater communication,which provides a theoretical basis for the selection of light sources for subsequent communication systems.(2)Analyzing the light-emitting principle and photoelectric characteristics of the light-emitting device LED,which focuses on the luminous efficiency in the optical characteristics of the LED and the modulation ability in the electrical characteristics,and puts forward the key role of the two characteristics in the realization of high speed transmission of visible light communication system.(3)The electrical channel of visible underwater communication system is analyzed,and the channel model based on IM/DD modulation mode is introduced.The relationship between the transmission SNR of the system and the average radiated power of the receiving and starting optical signals is analyzed,and the relationship between BER and SNR is further obtained.(4)The scheme design of the underwater video transmission system based on LED mainly realizes the selection of the receiving and transmitting devices and the design of the hardware circuit.Setting up a video signal transmission system to complete the transmission of LED blue light signals in air,pure water and simulated seawater.Through the comparison of experimental data in the three environments,the feasibility of blue light underwater transmission is verified.For the analog seawater transmission system,the signal can achieve 120 cm transmission(5)Testing the performance of the simulated seawater transmission system to test the relationship between different transmission distances,light receiving angles and background light to the system transmission error rate.Obtaining the change trend of the system performance through the change curve of the bit error rate.