Gaussian basis expansion phase noise suppression method for CO-OFDM systems.

In this paper, we propose a novel phase noise suppression method based on Gaussian basis expansion (GBE) for CO-OFDM systems. We analyze the basic phase noise suppression principle of GBE and then demonstrate it in optical OFDM transmission systems. Compared with common phase compensation (CPE), orthogonal basis expansion (OBE) and eigenvector basis expansion (EBE) schemes, the proposed GBE scheme has better phase noise fitting ability with similar computation complexity. Futhermore, no additional back to back (BTB) pre-training is needed for the GBE scheme. Performance improvements by the GBE is experimental validated in the QPSK/16-QAM OFDM system with different transmission scenarios (different number of pilots and input power). In the QPSK-OFDM system, after 160 km SSMF transmission, a Q-factor improvement of 1.7 dB and 0.5 dB are achieved compared with the CPE and OBE schemes at the optimum input power of -4 dBm, respectively. In the 16-QAM-OFDM system, the measured BER improved from 8.21×10-4 to 2.36×10-4 with the GBE scheme. To further verify the effectiveness of the GBE scheme, we change the laser linewidth and measure the long transmission distance performance by simulation, the results show that the GBE scheme can effectively increase the laser linewidth tolerance and extend transmission distance. When the linewidth is 2-MHz, the proposed GBE scheme can extend the transmission distance from 1120 km to 1540 km at the BER of 10-4. Experimental and simulation results show that the proposed GBE scheme is a promising alternative phase noise suppression for CO-OFDM system.