On the Benefits of Pre-Equalization for ACO-OFDM and Flip-OFDM Indoor Wireless Optical Transmissions Over Dispersive Channels

This paper analyzes the performances of indoor optical wireless data transmissions based on unipolar orthogonal frequency division multiplexing (OFDM). In particular, it is shown that using frequency-domain pre-equalization can provide benefits in terms of the reduction in the required optical transmit power for a given desired bit error rate (BER) from uncoded transmissions. Known for its power efficiency, asymmetrically clipped optical OFDM (ACO-OFDM) is considered as a unipolar modulation scheme for intensity modulation with direct detection (IM/DD). In addition, flip-OFDM is also considered as an alternative unipolar modulation scheme which is known to be as power efficient as ACO-OFDM. For both ACO-OFDM and flip-OFDM, analytical and simulation results show that using pre-equalization can save up to 2 dB of transmit optical power for a typical indoor optical wireless transmission scenario with the bit rate of 10 Mbps and the BER target of 10^-5.