Parallel Mini/Micro-LEDs Transmitter: Size-Dependent Effect and Gbps Multi-User Visible Light Communication

As an important supplement to radio frequency (RF) communication in a crowded indoor environment, high-speed multi-user visible light communication (VLC) is a promising candidate for practical application compared with point-to-point architecture. In this work, an area division concept is proposed based on the multi-directional low-cost array transmitter. For the first time, a series of parallel mini/micro-LEDs transmitters with various chip sizes are designed, fabricated and packaged, which are used to build a multi-user VLC link. The size-dependent characteristics of the parallel mini/micro-LEDs transmitters for VLC are systematically analyzed, including the linearity, electroluminescence, impedance, achievable bandwidth and data rate. The proposed transmitters with active regions of 75 μm, 100 μm, 125 μm, 150 μm, and 175 μm can provide access bandwidths of 278 MHz, 190 MHz, 133 MHz, 104 MHz and 85 MHz at 50-mA driving current for two independent users over a 3-m link, accordingly. The VLC system based on the parallel 75-μm micro-LED transmitter can simultaneously support two independent users at different positions with a summing data rate of 2.6 Gbps by implementing pulse-amplitude modulation 4-level (PAM4) schemes with Volterra equalizer. The maximum distance-rate product of 7.8 Gbps·m exhibits superiority to accelerate the practical deployment of high-speed multi-user VLC.