Demostration of 520 Gb/s/λ pre-equalized DFT-spread PDM-16QAM-OFDM signal transmission.

In this paper, we successfully transmit 8 × 520 Gb/s pre-equalized DFT-spread PDM-16QAM orthogonal frequency-division multiplexing (OFDM) signal over 840 km SMF with BER under 2.4 × 10(-2). We discuss how to obtain accurate tranceivers' response during pre-equalization for DFT-spread OFDM with coherent detection and we find conventional OFDM symbols training sequences (TSs) outperform DFT-spread OFDM symbols TSs in obtaining channel response for pre-equalization and equalization. Additionally, the optimal IFFT/FFT size is explored for the pre-equalized DFT-spread PDM-16QAM-OFDM transmission systems. It is the first time to realize 400 Gb/s/λ net rate OFDM signal transmission.