Minglun Zhang

Design of a visible light Internet access system

In this study, a visible light Internet access communication system is presented. The system uses visible light as downlink which can communicate at a distance of 2m. With the application of the pre-emphasis technology, a 3-dB transmission bandwidth of 130MHz is achieved. The physical layer of the system is controlled by FPGA (Field Programmable Gate Array) and the FPGA is the bridge of the MAC (Access Control Layer) and the physical layer. In the evaluation experiment the test computer can access Internet and play online video resources. The maximum downlink data rate is up to 30Mb/s.

An SDH off-line signal analysis software based on LabVIEW

SDH(Synchronous Digital Hierarchy) is one of the hot technology in optical fiber communication which has the large capacity and high data transmission rate, and it uses block frame structure to carry information. In this paper, a method of analyzing the structure of SDH frame by an off-line signal analysis software based on LabVIEW is presented. And this paper describes the implementation of lead-lag PLL(phase locked loop) in LabVIEW, which is the key technology used in the process of clock and data recovery.

High bandwidth based on a tapped delay line equalization in visible light communications

In the visible light communication, the white LED bandwidth severely limits the transmission rate of information. This paper presents an analog pre-equalization technology to compensate for the bandwidth of white LED. The technology not only can debug according to the actual channel changing, but also avoid the high costs of using FPGA technology. The pre-equalization technology is implemented by an analog circuit of tapped-delay-line, in the circuit we select an appropriate delay line and a digital to analog converter. In our LED visible light communication system, we can achieve a bandwidth of 150MHz，which was proved theoretically in the paper.