Beyond 400 Gb/s Direct Detection Over 80 km for Data Center Interconnect Applications

• Published in: Journal of lightwave technology Vol. 38; no. 2; pp. 538 - 545
• Main Authors: Le, Son Thai, Schuh, Karsten, Dischler, Roman, Buchali, Fred, Schmalen, Laurent, Buelow, Henning
• Format: Journal Article
• Language: English
• Published: New York IEEE 15.01.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Amplitude modulation; Bandwidth; C band; Calibration; Cloud computing; Computer architecture; Computer centers; Data center interconnect; Data centers; Data transmission; direct detection; Finite impulse response filters; Kramers-Kronig receiver; Optical communication; self-coherent detection; signal-signal beat interference cancellation; single side band transmission; Wavelength division multiplexing
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2019.2941690

Due to the growing demand for cloud services with high availability, high connection speed and low latency, distributed data-centers have emerged as a key architecture for future optical networks. This architecture relies on power and cost-efficient solutions for 400 Gb/s client interfaces over distances up to 80 km which can be densely wavelength-division multiplexed (WDM) in the C-band. Recently, single side band (SSB) direct detection (DD) has been considered as an attractive transmission scheme for achieving data rates beyond 100 Gb/s per channel due to its capability of electronic dispersion compensation. However, as SSB DD schemes utilize only a single polarization for data transmission, achieving 400 Gb/s per channel requires a baudrate beyond 80 Gbaud, which might reduce the effectiveness of the commonly used signal-signal beat interference (SSBI) cancellation techniques such as iterative SSBI cancellation or Kramers-Kronig algorithm due to the imperfection of Tx drivers, modulator and Rx front-end. In this paper, through effective Tx calibration and Rx DSP, we have achieved for the first time a net data rate per channel above 400 Gb/s with a 64 QAM signal at 85 Gbaud using a single photodetector (PD) at the receiver. In addition, a WDM transmission consisting of 5 channels at 100 GHz spacing was successfully conducted. This result indicates that SSB DD is an effective transmission technique for high capacity data center interconnect (DCI) applications.