OFDM for optical wireless systems under severe clipping conditions

In this paper, we analytically model the impact of clipping and quantization for optical wireless communication systems which employ direct-current biased optical orthogonal frequency division multiplexing (DCO-OFDM). Considering uniform quantization for both digital-to-analog converter (DAC) and analog-to-digital converter (ADC), analytical expression for signal-to-distortion-quantization ratio has been evaluated. A lower bound on required bit resolution for DAC/ADC, as a function of clipping ratio has also been determined for a target bit-error-rate (BER). Gain in modulation power at the output of the DAC under severe clipping conditions has been analytically evaluated. Furthermore, an iterative method for clipping mitigation is presented, which can be employed to relax the bit resolution required by the DAC, and further, to mitigate the clipping distortions.