Fig. 1. (a) Experimental setup of tricolor RGB LD-based bidirectional VLC system. (b) OFDM signal encoding and decoding processes. (c) Photography of tricolor RGB LD to produce white light. AWG, arbitrary waveform generator; PBS, polarization beamsplitter; DM, dichroic mirror; PD, photodiode; RTO, real-time oscilloscope; CF, color filter; AOM, acousto-optic modulator; ED, error detector; PPG, pulse-pattern generator; LPF, low pass filter.

Fig. 2. Experimental output optical power and biased current responses of the RGB LDs. Inset: measured optical spectra.

Fig. 3. (a) Measured SNRs and bit-loading of different OFDM subcarriers. (b) Constellation diagrams of 16, 32, 64, 128, 256-QAM of red LD.

Fig. 4. (a) Measured SNRs and bit-loading of different OFDM subcarriers. (b) Constellation diagrams of 8, 16, 32, 64-QAM of green LD.

Fig. 5. (a) Measured SNRs and bit-loading of different OFDM subcarriers. (b) Constellation diagrams of 8, 16, 32, 64-QAM of blue LD.

Fig. 6. Measured log(BER) of red LD at different received powers and influence on red LD with G/B LDs off and G/B LDs on.

Fig. 7. Measured log(BER) of green LD at different received powers and influence on green LD with R/B LDs off and R/B LDs on.

Fig. 8. Measured log(BER) of blue LD at different received powers and influence on blue LD with R/G LDs off and R/G LDs on.

Fig. 9. Measured Q-value of the remodulated upstream OOK signal (red points: 1 Mbit/s, blue points: 2 Mbit/s) against different received optical powers when different LPFs are used.