Research And Design Of Optical Transceiver In Visible Light Communication System Based On White LED

Visible light communication(VLC), a kind of wireless optical communication technologybased on white LED light source, has broad prospects for application which could be substitutedfor RF communications, especially on the occasion of strict restrictions about theelectromagnetic interference, such as airport, hospital etc. The research and development of VLCtechnology need low cost, small size and high gain optical receiver. The paper presents theoptical receiver based on Fresnel lens, which has simple structure and can meet the technicalrequirements of the VLC system.The paper first analyzes the basic technical requirements of the light source and opticalreceiver in VLC system. Advance a theory that using Fresnel lens as the optical collector toconverge the signal light, so the detector could receive more light energy. And two structureswith different receiving methods of the optical receiver were proposed. By measuring the spatialilluminance distribution of VLC system, the paper focuses on the impact of the multipath effecton system performance caused by wall reflection and multi-source. When there are fourreflection walls and four sources, 35.6% to 52.2% received light energy come from reflectedbeams in the area 0.5m near the walls, and about 21% to 35% in the other positions; In the 1mdiameter circulars just below the lights and the area around the walls, 4.9% to 29.1% of the totalreceived light is the direct light comes from the secondary sources, and other location about 30%to 58.8%.Fresnel lens designed by ZEMAX software has good converging performance with short focallength. The lens's size and convergence characteristics can meet the technical requirements ofoptical receiver in VLC system. The gain of received light energy using a single Fresnel lens wastested actually, when the lens collimate the light source, the detector can gain 1.36dB to 3.82dBfrom direct light, and the gain of the received light from the major sources can reach 3.87dB to5.06dB. The adverse effects of the wall reflection and multi-source on system performance arereduced, and it's helpful to overcome the multipath effects and increase SNR of the receiver. Thefeasibility and the benefit of collimated reception method with a single Fresnel lens is proved. Asimulation study on the multi-faceted optical receiver structure shows that the structure isinadequate for the optical receiver in VLC system.Finally, a novel optical transceiver is proposed which integrates the visible light reception withthe transmission of infrared light signal and preliminary study of the optical transceiver'sstructure was made by simulation.