Multimode and single-mode fibers for data center and high-performance computing applications

Abstract

Data center (DC) and high performance computing (HPC) applications have traditionally used a combination of copper, multimode fiber and single-mode fiber interconnects with relative percentages that depend on factors such as the line rate, reach and connectivity costs. The balance between these transmission media has increasingly shifted towards optical fiber due to the reach constraints of copper at data rates of 10 Gb/s and higher. The percentage of single-mode fiber deployed in the DC has also grown slightly since 2014, coinciding with the emergence of mega DCs with extended distance needs beyond 100 m. This trend will likely continue in the next few years as DCs expand their capacity from 100G to 400G, increase the physical size of their facilities and begin to utilize silicon-photonics transceiver technology. However there is a still a need for the low-cost and high-density connectivity, and this is sustaining the deployment of multimode fiber for links ≤ 100 m. In this paper, we discuss options for single-mode and multimode fibers in DCs and HPCs and introduce a reduced diameter multimode fiber concept which provides intra-and inter-rack connectivity as well as compatibility with silicon-photonic transceivers operating at 1310 nm. We also discuss the trade-offs between single-mode fiber attributes such as bend-insensitivity, attenuation and mode field diameter and their roles in capacity and connectivity in data centers.