Transmitter for Visible Light Communications Based on FPGA’s Output Buffers

Among the several new applications that Visible Light Communication (VLC) have made possible in recent years, board-to-board (B2B) communication represents an important field of employment for this technology. Most of the systems that would benefit from VLC-based B2B communication are digital boards that include Field Programmable Gate Arrays (FPGAs) or advanced processors. Modern FPGA output buffers have limited power, but switch at hundreds of MHz: a much higher rate compared to that of the typical single MOSFET employed in a ON-Off Key (OOK) transmitter. This letter explores the possibility of exploiting the FGPA buffers for realizing a OOK transmitter suitable for B2B communication. A transmitter circuit, driving a 70 mA LED, is proposed and characterized for 26 different electrical standards and configurations of the FPGA buffer. A 210Mb/s link was demonstrated at a distance of 6cm (120Mb/s at 24cm) with a Bit Error Rate (BER) ${\lt 1.5\cdot 10^{-6}}$ (95% confidence).