Two-Level Laser Diode Color-Shift-Keying Orthogonal-Frequency-Division-Multiplexing (LD-CSK-OFDM) for Optical Wireless Communications (OWC)

Optical wireless communication (OWC) technology has attracted many attentions recently. Lighting luminaries equipped with red-green-blue (RGB) based light-emitting-diodes (LEDs) or laser-diode (LDs) can modify the perceived color of illumination. These highly directional light sources with adjustable perceived colors makes them very suitable for high speed and high security data transmissions. Here, we propose and demonstrate a two-level LD based color-shift-keying orthogonal-frequency-division-multiplexing (CSK OFDM) signal for the OWC systems. This scheme cannot only provide non-flickering effect to minimize human health concern, but also can enhance the transmission data rate of the CSK system. Here, the system model and the implementation of bit and power loading algorithm on the LD-CSK-OFDM are discussed. Experimentally results show that the demonstrated LD-CSK-OFDM signal can achieve data rate of 28.4 Gbit/s with 1.25 m free-space transmission distance satisfying the forward-error-correction (FEC) threshold.