Improved Pilot-Tone Technique for Inter- and Intra-Channel Nonlinearity Compensation in Long-haul CO-OFDM Systems

摘要

This letter shows that coherent optical orthogonal frequency-division multiplexing (CO-OFDM) is a suitable modulation format for long-haul transmission when fiber nonlinearities are dominated. A combination of RF pilot (RFP) tone technique with various subcarrier filling schemes and various RFP guard band frame structure are studied. This technique is effective to combat inter- and intra-channel nonlinearity and enhance the performance of CO-OFDM system. The simulation results show an improvement in Q-factor tolerance due to laser phase noise and fiber nonlinearity compared to standard RF pilot technique. A transmission distance of 2400 km was considered, with the transmission over a standard single mode fiber (SSMF) with a nonlinear coefficient of 2.6×10~(-20) m~2/W. The compensation of the chromatic dispersion (CD) is carried out at the receiver. It is obvious that using only RF pilot technique is affected strongly by SPM induced mean nonlinear phase shifts from Q-factor plot. Partial carrier filling (PCF) technique is used here to improve the nonlinearity performance of the transmission.