As data center traffic increases, challenges rise for existing optical transceivers. For data center interconnects (DCIs) transmission distance matters and drives specifications of optical transceivers. For metro DCIs (>100 km), high bit rate and small form factor is imperative for next generation transceiver. On extended reach DCIs (<100 km) low cost and compact transceivers are a necessity and hence direct detection predominates over coherent detection. It is the overall aim of this work to investigate ways to enhance the optical transceiver higher data rate by considering novel architectures while considering proper transmission distance for each DCI applications.
In the case of metro DCI system, we propose a novel phase diversity concept to realize an arbitrary optical hybrid. The method allows a potential in a direct reduction of optical front-end complexity using single-ended detection. We also propose a systematic digital signal procecssing approach to achieve polarization division multiplexing of 400G per wavelength using conventional coherent reception. We demonstrate experimentally the recorded 448 Gb/s (56 Gbaud PDM-16QAM) transmission over 320 km employed digital-to-analog converters operating with sampling rate of 65.7 GS/s.
In the scenario of short reach DCI, we propose DSP algorithms to enable two, three and four dimensional modulation in direct detection transceiver. In particular, employing a dual-polarization Inphase-Quadrature modulator and a Stokes-vector receiver, we achieve the records of long reach transmission of 200 Gb/s, 300 Gb/s, and 400 Gb/s per wavelength for 2D, 3D, and 4D respectively. The results imply that our proposed work can quadruple the capacity of conventional intensity modulation/ direct detection at a longer transmission distance.