Modified constellation reshaping method for PAPR reduction of PDM CO-OFDM based on a SLM algorithm.

In this paper, we propose a modified constellation reshaping method for peak-to-average power ratio (PAPR) reduction in polarization division multiplexing (PDM) coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems based on the selective mapping (SLM) method. A modified quadrature amplitude modulation (M-QAM) constellation is generated that has the same minimum distance as that of the conventional QAM (C-QAM) constellation. The M-SLM method is denoted as the M-QAM constellations combining with the traditional SLM method. At the receiver side, the mean square errors between the constellations of the received data and each M-QAM rotated by different phase rotation factors are calculated. Then, the phase rotation factor with the minimum mean square error is selected to recover the original data. The advantage of the proposed method is that it does not need to send additional side information, while it possesses nearly the same PAPR reduction and bit error rate performance as the traditional SLM method.