Experimental Study Of Underwater Blue-Green Led Communication System

With the increasing scarcity of world resources,terrestrial resources have been unable to meet the needs of human development,so the utilization of marine resources has become particularly important.At the same time,with the deepening of human development of marine resources,the traditional underwater communication methods have been difficult to meet the actual needs.Therefore,further research is needed on the underwater wireless optical communication(UWOC)with fast communication rate,long distance and low delay to make up for the shortcomings of traditional communication methods.In this paper,based on the background of UWOC,the experimental research of the underwater blue-green optical communication system is carried out.This paper mainly research in the following points:1.According to the.channel characteristics of light in seawater,the optical characteristics of light in seawater are analyzed,and the absorption and scattering characteristics of pure seawater,phytoplankton,yellow substances and suspended particles in seawater are introduced in detail,and the LED(Light Emitting Diode,LED)transmission model of light source in water and signal-to-noise ratio and bit error rate of communication system is established.2.In this project,green LED with a peak of 530nm is used as the emission light source of the underwater blue-green light communication system,and the combination of reflector cup and condenser lens is used to realize the condensing and collimation of the light source.The LED driver circuit design scheme suitable for the transmitter of the underwater communication system adopts TPS61500 as the driver chip of the driver circuit.3.This paper proposes a design scheme of a wide-angle focusing double-layer fly-eye lens optical system.According to the geometrical optics principle of the lens array,the fly-eye lens receiving system is designed and simulated by Zemax.An experimental device for measuring the receiving efficiency of the underwater communication system is built,and the optical power of the receiving optical system is experimentally measured.Within the link distance of 1m,3m and 5m,the double-layer compound eye system receives more light than the single-layer compound eye system.Power values have been increased by 60%,59%and 57%respectively.The results show that the double-layer fly-eye lens receiving antenna can significantly improve the optical power value received by the receiving end.4.Completing the hardware assembly and debugging of the hardware circuit of the transmitter and receiver,using the signal generator and oscilloscope to conduct experiments on the transmission of the system baseband signal,and using the optical power measuring instrument to measure and analyze the optical power value received by the system,the feasibility of the design scheme of the transmitter and the receiver is verified by debugging experiments.In the water tank and water pipe in the laboratory respectively,the experimental test of the communication performance of the system with different turbidity and different communication distance is carried out.The modulation method used in the experiment is OOK modulation.The experimental results show that in the clean water environment with a turbidity of Omg/L,the communication system can complete the transmission of communication data well,the communication bit error rate is 4.46×10-15.With the increase of turbidity,the communication waveform is gradually distorted,and the communication bit error rate also increases.When the turbidity increases to 10mg/L,the communication bit error rate also increases to 5.28×10-12.When the turbidity exceeds 10mg/L,the system will not be able to achieve communication transmission.In the clean water environment with turbidity of Omg/L,the communication distance of the system is increased from 1m to 5m,the amplitude of the received communication waveform is reduced from 206mV to 7.84mV,and the bit error rate of the communication system is reduced from 1.36×10-14 increased to 4.58×10-12.When the modulation bandwidth is 10MHz,the amplitude of the communication waveform is 20.88mV,and the complete waveform data can be received.In summary,the underwater blue-green optical communication system designed in this paper can realize the underwater wireless optical communication with a modulation rate of 10MHz and a communication distance of 5m.