We propose a novel discrete Fourier transform (DFT) spread M-ary amplitude shift keying (M-ASK) coherent optical orthogonal frequency division multiplexing (CO-OFDM) with a Hermitian symmetry system to mitigate nonlinear effects by reducing the peak-to-average power ratio (PAPR) of the OFDM signals. The proposed DFT-spread M-ASK CO-OFDM with the Hermitian symmetry system has a lower PAPR than the conventional M2-quadrature amplitude modulation (QAM) CO-OFDM system using the DFT-spread scheme. Furthermore, to reduce the PAPR further as compared to the DFT-spread M2-QAM CO-OFDM system, the proposed system uses the Hermitian symmetry of the DFT, which enables the proposed system to have a lower modulation order of M instead of M2. The significantly reduced PAPR of the proposed system provides superior nonlinear tolerance. We analytically investigate the PAPR distributions of the OFDM systems. We also perform numerical simulations to investigate the PAPR characteristics and nonlinear tolerance of the OFDM systems. Our numerical results show that the proposed system outperforms the conventional CO-OFDM and DFT-spread CO-OFDM systems in terms of the bit error rate and PAPR.
Bibliographical noteFunding Information:
This work was supported in part by Brain Korea 21 plus project in 2013, and in part by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology under Grant 2013R1A1A2009689.
© 2013 Elsevier Inc.
- Coherent communications
- Fiber-optic transmission systems
- Optical nonlinear effect
- Orthogonal frequency-division multiplexing (OFDM)
- Peak to average power ratio (PAPR)
ASJC Scopus subject areas
- Control and Systems Engineering
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering