A Power-Efficient SDM Structure for Next-Generation Data Center Interconnect

Coherent detection increases system capacity and can be combined with multi-channel structures, such as space division multiplexing (SDM), to push to the 1.6 Tbit/s required by future data center interconnects (DCIs). We present a methodology for finding a power efficient SDM multi-channel structure for a given traveling-wave Mach-Zehnder modulator (TW-MZM) design, as specified by its experimentally measured time and frequency domain properties. We focus on silicon photonics (SiP) solutions in our examples, due to their potential for high-scale integration and low cost. We simulate each channel of an SDM structure, considering the hardware characteristics and digital signal processing (DSP) performance enhancement, for an end-to-end system examination. We find the amount of parallelism that yields the lowest combined laser and RF drive power. The choice of operating point (drive voltage) and the judicious use of DSP and clipping must be optimized independently for each SDM structure. For the two SiP modulators examined, we find an SDM structure with three channels consumes the least amount of power among all multi-channel solutions, and saves up to 59% of consumed power vis-à-vis the single-channel solution.