Key Technologies for High-Speed Si-Substrate LED Based Visible Light Communication

Nowadays, the demand for high-speed information transmission is increasing rapidly. Visible light communication (VLC) based on light-emitting diodes (LEDs) is supposed as a potential candidate for future 6G communication networks. However, as an emerging field of optical communications, the data rate of VLC systems is restricted to the extremely limited modulation bandwidth and nonlinear characteristics of optoelectronic devices. In this paper, we outline the state of art and challenges of VLC, and introduce the key technologies for high-speed Silicon (Si) -substrate LED-based VLC systems. Based on an optimized integrated 4x4 8-wavelength LED array and advanced digital signal processing (DSP) methods, we demonstrate an ultrahigh-speed VLC system. Digital Zobel network (DZN) pre-equalization and transfer learning bidirectional gate recurrent unit (TL-Bi-GRU) based post-equalization are proposed to mitigate linear and nonlinear impairment. The yellow and green LEDs are especially enhanced in high-efficacy, and achieve the impressive data rates of 3.45 Gbit/s, and 3.83 Gbit/s respectively, which is a remarkable improvement. The achievable overall data rate of the device is 28.93 Gbit/s. As far as we know, it's the highest data rate achieved by a single-chip Si-substrate LED array.