Design And Implementation Of Visible Light Broadband Data Communication System

In the special situation of high-voltage transmission line,aircraft,high-speed rail and other strong electromagnetic interference,the traditional wireless communication will be greatly limited.As a new communication technology,visible light communication can replace the traditional wireless communication in the strong interference situation because of its special transmission mode.At present,visible light communication technology is still in the development stage.Most of the existing achievements are only suitable for the ideal environment of the laboratory,so it has poor practicability and popularization.Due to the problem of limited application scene of visible light,this paper designs and implements a broadband visible light communication system with a wide range of application scenes.This system can be combined with a wide range of civil lighting,so that the light can transmit data information while lighting,and realize the perfect integration of lighting and communication.In this paper,the basic concepts of optical transmission are briefly introduced.Based on the characteristics of optical devices,the factors that restrict the transmission bandwidth and transmission distance of traditional optical communication links are analyzed,and the practical scenarios are combined.While ensuring real-time communication,the visible communication system that can improve the transmission bandwidth and transmission distance of links is researched and designed,which can be used in a wide range of occasions.First of all,a set of low-cost and simplest system is designed to realize a simple and practical visible light communication system by making full use of the advantages of OOK modulation.The data rate can reach 7mbps at the distance of 50 m outdoors,which can apply to various actual occasions.In this system,LED light is used as the light source at the sending end,and Fresnel lens converges the light into a beam;in the receiving end,the influence of ambient light is removed,the channel equalization is processed,and the waveform recovery and reconstruction are completed.Then,based on the improvement of this system,a design link of visible light communication based on pre emphasis is proposed,which mainly improves the driving mode of LED and the signal processing of the receiving circuit.Compared with the OOK modulation,the communication bandwidth can be increased by more than ten times.The LED lamp is also used as the light source at the sending end in this link,and the pre emphasis mode at the sending end is proposed to compensate the bandwidth of the LED lamp and at the receiving end.The application of post equalization technology compensates the bandwidth of photodiode,greatly expands the bandwidth of communication link,and realizes high-speed data transmission.The design and measurement of this subject show that the visible light communication system based on OOK modulation in the outdoor midday sunlight or night can achieve both 7mbps real-time stable transmission at 50 m transmission distance,and 1Mbps real-time stable transmission at 70 m transmission distance.The improved visible light communication system based on pre emphasis can improve the real-time communication bandwidth to 130 Mbps.The communication system designed in this paper can communicate normally in many specific environments,and has a wide range of application scenarios.The system has a high directionality and security.At the same time,it has the characteristics of low cost,superior performance and high use value.