Coherent Data Center Links

As link bit rates within and between data centers continue to increase, it is challenging to maintain low power consumption while accommodating ever-tighter optical link budgets. Although power consumption can be reduced by co-packaging optical transceivers with electrical switches and employing optical switching, both approaches increase losses, further compressing link budgets. Local oscillator-based coherent receivers traditionally employed for long-haul systems provide a path to higher bit rates and improved link budgets, but their power consumption is excessive owing to high-speed digital signal processing (DSP). We discuss alternative designs for coherent receivers, such as DSP-free coherent receivers and Kramers–Kronig (KK) receivers. We compare them in terms of receiver sensitivity, power consumption, and complexity.