Link technologies in today's data center networks impose a fundamental trade-off between reach, power, and reliability. Copper links are power-efficient and reliable but have very limited reach (< 2 m). Optical links offer longer reach but at the expense of high power consumption and lower reliability. As network speeds increase, this trade-off becomes more pronounced, constraining future scalability.

Mode-division multiplexing (MDM) using few-mode fibers (FMFs) appears as a promising technology to increase fiber capacity by a few orders of magnitude and sustain the traffic demand for the decades to come. The potential of MDM lies in its ability to exploit multiple modes within a single optical fiber strand. Since 2011 and the first promising demonstrations, impressive progress has been made. In this article, we will show how the most recent advances in design and fabrication have improved the performance of FMFs and MDM systems, and allowed to turn research demonstrations into practical deployments.