Research On Key Technologies Of Visible Light Communication

Visible light communication is a high-speed stroboscopic signal that is invisible to the human eye by a visible light source such as a light-emitting diode to transmit information.It has the advantages of no electromagnetic pollution,no need for spectrum resource authentication,and strong confidentiality.This paper mainly studies the multi-lamp full-duplex visible light communication system,which has a large communication coverage,is compatible with 100 M Ethernet,and the communication transmission distance reaches 3meters.In addition,this paper focuses on the modulation method DCO-OFDM technology commonly used in visible light communication systems.The modulation scheme is given and the logic simulation is implemented in the FPGA development environment.The main innovation of this paper is the multi-lamp based visible light communication system.The system adopts full-duplex design.The downlink uses 12 strings of 2 LEDs as the communication light source,which is fully compatible with the lighting requirements,and the uplink uses 650 nm red laser as communication light source.The electric port module and media conversion circuit are used to fuse visible light communication system with Ethernet.The electrical signal sent by the Ethernet signal/terminal is transmitted in the free space by the high-speed modulation of the LED/LD,and is received and recovered by the receiving end.This paper introduces the key technologies of the multi-lamp system.In the choice of modulation method,OOK modulation method is adopted in consideration of practical problems such as system cost,hardware implementation complexity and heat dissipation.In bandwidth expansion,the transmitting end is designed with pre-emphasis circuit,and the receiving end is designed with post-equalization circuit.The system bandwidth is extended from 3MHz to 133MHz;in the multi-lamp drive design,a differential drive module and a current amplification module are designed.The experimental platform of multi-lamp system was built.System bandwidth,network access indicators,bit error rate,PC Internet access and communication coverage were tested in turn.Finally,the design scheme of the DCO-OFDM baseband system,as well as the principleand implementation method of each module,and the simulation test results in the FPGA development environment are introduced.