1.57 Tb/s PDM-layered 80QAM-OFDM in super-channel transmission based on self-homodyne comb

摘要

In this paper, polarization division multiplexing-layered 80-ary quadrature amplitude modulation-orthogonal frequency division multiplexing (PDM-layered 80QAM-OFDM) is proposed and demonstrated in super-channel system based on self-homodyne comb. The composition of the super-channel is derived from the optical comb generated by a single laser-driven dual polarized Mach-Zehnder modulator (DP-MZM) modulated by odd side -band suppression. Since the optical comb generated by the transmitter is used as a local oscillator (LO) signal for self-homodyne coherent detection. This scheme effectively reduces the system cost and alleviates the perfor-mance constraints caused by phase noise. Moreover, the bit error rate (BER) and generalized mutual information (GMI) of layered 24QAM/48QAM/80QAM-OFDM are evaluated to obtain the highest transmission rate and the laser linewidth tolerance of the system. The results show that in Additive White Gaussian Noise (AWGN) channel, layered QAM signal realized by low-complexity constellation layering technique can significantly improve the BER performance at a small entropy cost compared with ordinary QAM signals. Meanwhile, the layered 80QAM can achieve a signal-to-noise ratio (SNR) gain of 2.7 dB. In addition, after 40 km standard single mode fiber (SSMF) transmission, the total data rate of the system can reach 1.57 Tbit/s and the corresponding spectral efficiency (SE) is 12 bit/s/Hz when the BER of the super-channel system meets soft decision-forward error correction (SD-FEC) threshold.