Optical Transmission Systems for Data Center Networks

Research Scope The project targets the investigation of optical transmission systems for data center networks (>800 Gb/s data rate) and a reach of 10 km or more. Applications include mega data centers with multiple large data centers collocated on a single campus (e.g. Facebook Ireland DC in Clonee with 2 hyperscale DCs to be extended to 5 DCs). To achieve 800 Gb/s, one may consider a multi-lane approach with four channels of >200 Gb/s net data rate each over a single fiber on a CWDM grid. Communication should be based on intensity modulation and direct-detection (IM/DD). Research Goals Different technological approaches should be compared and a clear recommendation made on which technological path is best. Candidate modulations may include PAM6 and PAM8 formats. To achieve the target data rate, various signal processing schemes should be investigated including linear and non-linear precoding, and near-coherent-rate receivers with oversampling. Computational and implementation complexity should be considered and compared. To improve the end-to-end bit-error rate, advanced coded modulation formats should be included in the system design. To deal with the chromatic dispersion penalties for longer reach channels, dispersion pre-compensation schemes requiring complex field modulations should be investigated. These may be realized using, e.g., a standard dual-drive MZM or an IQ-modulator. The receiver should use direct-detection to keep the costs low, but the receiver may use advanced signal processing in combination with oversampling. All results should be investigated numerically as a proof-of-concept. In a second stage of the project, the methods should be verified by laboratory experiments.