Energy Efficient High Capacity Coherent WDM and DCIs

Hyperscale data centers (HDCs) will drive internet traffic to an astounding 20 zettabytes by 2021 and will represent 53 percent of all installed data centers [CISCO Visual networking Index]. HDCs are expected to drive the ethernet engines of the data center interconnect (DCI) to scale from 12.8 Tbps today to over 100 Tbps pushing the limits of today’s non-coherent systems in terms of power dissipation and density. One solution is to bring coherent wave-division-multiplexed (WDM) links (multiple optical channels operating in parallel over the telecommunications band) into the intra-DCI regime (< 2km). However, power hungry electronics in today's coherent optical architectures such as those associated with digital signal processing (DSP) or high bandwidth optical- and electronic- phase locked loops (OPLLs, EPLLs) must be eliminated and alternative techniques employed.

We are developing the FREquency Stabilized Coherent Optical (FRESCO) link that leverages low-noise laser technologies from precision scientific applications such as optical-frequency transfer over fiber and atomic clock synchronization, employed in the ultra-high capacity optical communications context for the first time. By using state-of-art low phase noise integrated lasers in place of standard commercial 'noisy' lasers, we begin to eliminate certain complex and power hungry circuitry typically required for link operation.  Further, these FRESCO transceivers can be sourced by a single low-noise laser by 'cloning' itself for multiple WDM channels using nonlinear frequency comb techniques also investigated here in the OCPI group resulting in a 'shared source' operation that further drives down system complexity, cost, and power.  A vision figure of the fully integrated FRESCO transceiver in SiPh/SiN and Bi-CMOS is presented below as a novel approach to low-power, ultra-high data rate optical communications and promising candidate for future Tbps data center interconnects.