Fig. 1. Measured optical power against LED current.

Fig. 2. SNR versus subcarrier frequency (LED channel response and channel pre-compensation).

Fig. 3. Measured output power spectrum: (a) 10 and (b) 50 MHz (sinusoidal signal of 1.1 V at the bias current of 100 mA).

Fig. 4. Schematic of adaptive pre-compensation for our OFDM system. AMP, amplifier; LPF, low-pass filter; P/S, parallel to serial; S/P, serial to parallel.

Fig. 5. Experimental setup of LED communication.

Fig. 6. Measured power spectrums of OFDM symbols: (a) without pre-equalization (driving signal from PA); (b) without pre-equalization (received signal from PD); (c) with pre-equalization (driving signal from PA); (d) with pre-equalization (received signal from PD).

Fig. 7. Measured BER versus bias current with pre-compensation.

Fig. 8. BER versus the OFDM signal power with 32-QAM.

Fig. 9. BER versus the OFDM signal power with 64-QAM.