DFT-OFDM systems with real modulation and DC-biasing for intensity modulated direct-detection optical communications

This paper investigates discrete Fourier Transform (DFT)-precoded OFDM systems (DFT-OFDM) for intensity modulated direct-detection optical communications. Such scheme can be used to support both single and multiple user communications. Two DFT-OFDM systems using real modulation and DC-biasing are proposed. Performance analysis based on signal-to-interference-and-noise ratio (SINR) is provided. Insights are provided for designing choices between different modulations, and between using DC-biasing and asymmetrical clipping approaches. Simulation results show that the proposed schemes largely outperform systems using asymmetrical clipping, particularly in the case of using higher order modulations.