Performance of 16 QAM-OFDM with new null subcarrier shifting in an intensity-modulated direct detection system

To reduce the peak-to-average power ratio (PAPR) of the optical orthogonal frequency-division multiplexing (OOFDM) signal, a novel null subcarrier shifting scheme is proposed in an intensity-modulated direct detection OFDM system. At the receiver, a constant subcarrier is used as the location information to implement demodulation accurately. Meanwhile, the computational complexity is degraded apparently by adopting the proposed scheme. The experimental results show that the PAPR reduction of the OFDM signal can reach about 2 dB at a complementary cumulative distribution function of 1 × 10^-4, and the receiver sensitivity after 100 km single-mode fiber transmission at the bit error rate (BER) of 1 × 10^-3 can be improved by about 1.5, 1.8, 2.1, and 2.6 dB when the launch power is 3, 5, 8, and 10 dBm, respectively.