The performance of high data rate QPSK channels is impaired by cross-phase modulation (XPM) induced by lower rate optical orthogonal frequency division multiplexing (OFDM) channels in hybrid wavelength division multiplexed (WDM) systems. Given that XPM-induced phase noise is the dominant impairment, a combination of OFDM and double sideband modulation is presented in this paper to mitigate XPM-induced phase noise, which is investigated in frequency domain and time domain.
Monte Carlo simulation results indicate that the variance of XPM-induced phase noise can be reduced with intermediate frequency (IF) of optical OFDM increasing and the BER performance of QPSK signal can be improved.