Comparison of OFDM and OFDM/OQAM Systems in Nonlinear Interference

Coherent optical orthogonal frequency-division multiplexing (CO-OFDM) divides the high speed optical signals into several low speed orthogonal sub-carriers. With the insert of cyclic prefix (CP) between consecutive OFDM blocks for the inter-symbol-interference (ISI) induced by chromatic dispersion (CD) and polarization-mode-dispersion (PMD) could be combated. CO-OFDM achieve high spectral efficiency. With the increase of transmission distance, the channel memory length increases with the accumulation of CD and PMD, the system spectral efficiency deteriorates accordingly. Orthogonal frequency-division multiplexing offset-quadrature amplitude modulation (OFDM/OQAM) removes the CP inserted to increases the system spectral efficiency. Nonlinear effect includes self-phase modulation (SPM) and cross-phase modulation (XPM) induced by Kerr effect of fiber channel has great influence on OFDM and OFDM/OQAM in long distance transmission. We systematically analyze the ability of CO-OFDM system and CO-OFDM/OQAM system to resist the nonlinear interference for the first time. The establishment of mathematical model is based on Volterra series. Simulation shows that CO- OFDM/OQAM system has strong resistance to nonlinear interference.