Research On High Speed Transmitter Technology In Visible Light Communication System

Visible light communication technology uses light as the information carrier for communication transmission.Compared with traditional communication methods,visible light communication has rich spectrum resources and no need to apply.In addition,it has the advantages of antielectromagnetic interference and green environmental protection and has been widely studied and applied.The main body of the visible light communication system can be divided into three parts:optical transmitter,channel and optical receiver.The performance of optical transmitter directly determines the advantages and disadvantages of visible light communication system.This topic takes LED and LD as the light source respectively to study the circuit design of high-speed optical transmitter and complete the development of prototype under the condition of considering communication distance and communication speed.At the same time,the communication rate of the transmitter is further improved by pulse amplitude modulation.The main innovation points and work contents are as follows:1.Using LED as the transmitter light source,the pre-weighted technology and driving technology are studied,and the hardware preweighted circuit and driving circuit are designed to expand the modulation bandwidth of LED.The experimental results show that the-3dB bandwidth of the LED transmitter is increased from 13.5MHz to 303MHz,and the real-time transmission experiment of 500Mbps and zero bit error rate is realized under the indoor distance of 2m,and the real-time transmission experiment of 750Mbps under the forward error correction tolerance.The shell structure is designed and the prototype of LED transmitter is developed.2.Using LD as the transmitter light source,the laser diode driving technology was studied,and the high-speed LD transmitter circuit was developed.The real-time transmission experiment of 1.8Gbps with zero bit error rate was completed at lm distance in the room,and the real-time transmission experiment of 2.5Gbps was completed under the forward error correction tolerance;3.Studied the pulse amplitude modulation technology,developed PAM4 code type LED transmitter circuit,innovatively proposed the method of using FPGA circuit and RF comber to generate PAM4 signal,and used PAM4 modulation circuit in LED transmitter for real-time transmission experiment.The experimental results show that the eye image is clearly visible when the PAM4 signal of 3 50Mbaud is transmitted.