Analysis of DCO-OFDM and flip-OFDM for IM/DD optical-wireless system

The paper analyzes the performance of two forms of orthogonal frequency division multiplexing (OFDM) techniques called as DC biased Optical OFDM (DCO-OFDM) and Flip- OFDM for intensity modulated direct detection (IM/DD) system. The aforementioned OFDM schemes are compared in terms of peak-to-average power ratio (PAPR) and bit error rate (BER) as a function of electrical energy per bit to noise power ratio (E_b(elec)/N₀) when the signal is affected by additive white Gaussian noise (AWGN). In particular, 7-dB and 13-dB DC bias are used for DCO-OFDM in BER analysis and finally compared with flip-OFDM for the different data formats such as 4-,16-,64-,256- QAMs. The results show that flip-OFDM performs better in BER analysis with reduced value of (E_b(elec)/N₀) and thus, it can be considered as a power efficient unipolar modulation format. However, Flip-OFDM signal provides a high PAPR value that can deteriorate the overall system performance. Finally, OFDM signal performance tradeoff is measured as a function of transmitted optical power, QAM size, and spectral efficiency.