Single-Carrier and Multi-Carrier 400 Gbps Transmission With Multi-Rate Multi-Format Real-Time Transceiver Prototypes

New customer usages such as on-demand high-definition videos, business analytics, and cloud services stress more and more optical transport networks. While 100 Gbps WDM systems have been widely adopted by operators to cope with the capacity growth of the past 6-7 years, a new generation of the optical transmission system is required to respond to the exponential traffic demands coming from mobile, fixed, and data center networks. Equipment manufacturers recently planned to enhance to 400 Gbps the data rate carried by WDM channels to meet this ever-increasing traffic requirement. Various trends are in competition to achieve this objective. Single-carrier and multi-carrier techniques operating at different symbol rates (i.e., 32, 45, > 60 Gbaud) and with diverse modulation formats (DP-QPSK, DP-8QAM, DP-16QAM) are proposed depending on whether transmission distance, spectral efficiency, or cost is the predominant driver. In this paper, we investigate the potential of these various 400 Gbps solutions by using real-time transceiver prototypes generating 32/64 Gbaud DP-QPSK, 45 Gbaud DP-8QAM, 32/61 Gbaud DP-16QAM formats over various fiber types (i.e., G.652, G.654, G.655 fibers). In particular, we demonstrate 400 Gbps WDM transmission with 61 Gbaud DP-16QAM channels using bandwidth-limited DAC/ADC (i.e., <; 15 GHz) and real-time signal processing based on maximum likelihood sequence estimation equalization that mitigates bandwidth limitations. We conclude by analyzing the fiber non-linearity robustness of the 400 Gbps real-time transceivers under test thanks to the Gaussian noise model that permits to extract the ANL parameter and quantify non-linear interference affecting optical channels after fiber propagation.