Channel Capacity of IM/DD Optical Communication Systems and of ACO-OFDM

In this paper, the authors investigate the channel capacity of Intensity Modulated Direct Detection (IM/DD) wireless optical communication systems for an AWGN channel with a limit on the average transmitted optical power. It has recently been shown that Asymmetrically Clipped Optical Orthogonal Frequency Division Multiplexing (ACO-OFDM) is more efficient in terms of optical power than conventional optical modulation techniques such as Pulse Position Modulation (PPM). When ACO-OFDM is used, the transmitted signal has a clipped Gaussian probability distribution. They calculate the channel capacity for systems using transmitted signals with exponential and clipped Gaussian distributions, and for an ACO-OFDM system.