Supporting the ever-increasing data-center-inter-connect traffic in a cost-effective manner is a great challenge, which requires innovative transmission and digital signal processing (DSP) techniques. Recently, single-side-band (SSB) direct-detection (DD) transmissions have been actively considered for data rates beyond 100 Gb/s per channel and distance of hundreds of kilometers due to its capability of electronic chromatic dispersion compensation. In addition, several effective DSP techniques to mitigate or suppress the signal-signal beating interference (SSBI) due to the squared-law detection of the photodiode have been intensively investigated, such as Kramers-Knonig (KK) and SSBI cancellation schemes, showing promising performance at data rates over 200 Gb/s and distance beyond 100 km. In this paper, we demonstrate that high-performance low-complexity SSB DD transmissions can be achieved by generating a digital carrier (virtual carrier) together with the complex information-bearing signal at the transmitter using only two digital-to-analog converters. Combining this transmission technique with either the KK field reconstruction or a two-stage SSBI cancellation scheme at the receiver, eight-channel WDM signals with a net data rate of 1.72 Tb/s have been transmitted successfully over a record span length of 200 km at 1550 nm.
