Study of the Feasibility of Multi-channel WDM Transmission Using RGB LEDs in Visible Light Communication

In recent years, the proliferation of digital communication systems has been fueled by the increasing use of connected devices in both consumer and industrial sectors. The predominant reliance on radio frequency communication for data transfer faces challenges due to physical limitations and regulatory restrictions on frequency ranges. Responding to these challenges, Visible Light Communication (VLC) has emerged as an innovative solution, utilising the visible light spectrum to modulate the intensity of light emitted by sources like white LEDs. This paper explores the feasibility of employing Red/Green/Blue (RGB) LEDs for three-dimensional visible light communications using off-the-shelves equipment. This type of communication is known as Wavelength Division Multiplexing (WDM) as data is encoded in the three colour wavelength. On-Off Keying (OOK) is used as modulation on each wavelength. Afterwards, the more efficient Orthogonal Frequency Division Multiplexing (OFDM) modulation scheme is explored. The implemented solution involves three emission circuits, each modulating the one colour component of the RGB LED current. The receptions side involves dichroic R/G/B colour filters and a Transimpedance Amplifier (TIA) circuit, with a Raspberry Pi 4 facilitating offline data decoding sampled by an Arduino UNO. The prototype demonstrates successful VLC communication with OOK modulation at distances up to 1.5m for red and blue LEDs and 0.75m for green LEDs, achieving data rates up to 800 bit/s.