There exists a demand for radiation-safe and high-speed communication systems available to public users in the fifthgeneration (5G) communication and beyond. In this regard, visible light communication (VLC) stands out offering multi-Gigabit-per-second (Gbit/s) data transmission, energy efficiency and illumination, while being free from electromagnetic interference. Here, we report a high-speed VLC link by using a 443-nm GaN-based superluminescent diode (SLD) and bit-loading discrete-multiple-tone (DMT) modulation. Analysis of the device characteristics and modulation parameters shows a feasible bit allocation of up to 256-QAM while obtaining up to 3.8 Gbit/s data rate. These results, together with the electro-optical properties of the SLD such as being droop-free, speckle-free and high-power, make it an attractive solution for the future of public communications and smart lighting, while complementing traditional fiber-based and millimeter-wave technology.