PAPR reduction technique by inserting a power-concentrated subcarrier for CO-OFDM

Optical orthogonal frequency division multiplexing (OFDM) signals suffer from the nonlinear effects of an electric-to-optical modulator and fiber due to high peak to average power ratio (PAPR) characteristics. We propose a power-concentrated subcarrier method for use in OFDM systems to reduce PAPR of the OFDM signal without increasing system complexity or side information. The PAPR can be reduced by simply inserting a power-concentrated subcarrier (PCS) to replace the zero in the end of the signal spectrum at the zero padding stage. The simulation is performed with a conventional CO-OFDM transmission system with a PCS under dispersion and a nonlinear effective fiber to estimate PAPR using complementary cumulative distribution function (CCDF), error vector magnitude (EVM), and bit-error-rate (BER) characteristics. After a 2000-km transmission, the conventional CO-OFDM had an optimal fiber launch power of −6 dBm from the BER characteristics. In contrast, the proposed CO-OFDM with a PCS improves transmission performance in terms of log(BER) as much as −0.67 by an increased fiber launch power of −1 dBm with 60% concentrated-power of the PCS.