Polarity separating optical orthogonal frequency division multiplexing for free-space visible light communications

A modulation format, polarity separating optical orthogonal frequency division multiplexing (PSOOFDM), is proposed to mitigate the light-emitting diode (LED) nonlinearity for visible light communication systems. A polarity separator is used to divide the OFDM signal in time domain x(t) into two parts: x(+)(t) and x(-)(t), which will be transmitted parallelly from the different LEDs and overlap linearly in free space to realize PSO-OFDM. The experimental results demonstrate that PSO-OFDM has high spectral efficiency and suffers less nonlinear distortions than other methods. Employing PSO-OFDM, the modulation index and bit error rate performance can be significantly enhanced. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE).