Compact Speed: How 100G IR4 Enables High-Density ToR Switching
As data centers evolve to support high‐performance computing (HPC) and AI workloads, Top‐of‐Rack (ToR) switch deployments demand ever‐greater bandwidth in ever‐smaller physical footprints. Traditional 10G or 40G links can quickly become insufficient, while 100G ER4 or coherent optics add cost and complexity. Enter the 100G IR4 optical transceiver—a powerful, mid‐reach solution that delivers 100 Gbps over single‐mode fiber up to 2 km. In this article, we explore how 100G IR4 transforms ToR switching by offering space savings, simplified cabling, and the performance needed for dense, compute‐intensive clusters.
Solving the Density Dilemma
Modern ToR switches often sport 32 to 48 SFP+ ports for 10 Gbps or 12 to 16 QSFP+ ports for 40 Gbps. These ports consume valuable front‐panel real estate and consume significant power. By deploying QSFP28 IR4 modules, each supporting four 25 Gbps lanes on a single duplex LC interface, data center operators can repurpose QSFP28 ports—replacing multiple 10 Gbps uplinks or even freeing QSFP+ slots—while maintaining or increasing per‐rack aggregate bandwidth. This “port consolidation” reduces switch hardware requirements and enables racks to host more servers or accelerators without sacrificing network performance.
Streamlined Cabling in Tight Spaces
ToR deployments must balance cable management, airflow, and ease of maintenance. 100G IR4 uses duplex LC connectors on standard single‐mode fiber (OS2), in contrast to bulkier MPO‐based solutions. Since OS2 fiber and LC patch cords are widely available and familiar to operations teams, 100G IR4 lanes can be patched using existing fiber panels and breakout cables. For example, a 100G IR4 link can be broken out into 4×25G paths with inexpensive LC‐to‐LC splitters—ideal for connecting multiple downstream devices or NICs. The result is cleaner cable runs, fewer strain points, and better rack airflow—critical in high‐density environments.
Mid‑Reach Flexibility for AI and HPC
HPC clusters and AI training pods often span multiple cabinets or even separate rows, requiring reliable connections up to 2 km. 100G ER4 modules can cover these distances, but ER4’s 40 km reach comes at a premium power and cost. 100G IR4, designed for ∼2 km reach, offers a sweet spot: enough distance for typical campus or row‐adjacent cabinets, yet with lower power (<4.5 W) and reduced bill of materials. This makes IR4 a cost‐effective and energy‐efficient choice for mid‐reach ToR interconnects in AI racks, where collocated GPU servers demand ultra‑low latency and high throughput.
Power and Thermal Benefits
Dense racks filled with GPUs, FPGAs, or storage arrays generate significant heat. Network transceivers contribute to the thermal load; thus, selecting optics with lower power consumption can make a big difference. Compared to coherent modules (6–8 W) or ER4 (5–6 W), 100G IR4’s typical power draw of 4–4.5 W per port helps reduce cooling requirements. Over dozens of uplinks, this yields meaningful operational savings and improves rack‐level thermal management, enabling higher compute density without thermal throttling.
Future‑Proofing the Edge
As AI algorithms and data sets grow, so too will network demands. By integrating 100G IR4 today, data centers prepare ToR architectures for straightforward future upgrades to 200G or 400G, since many switch platforms support backward‐compatible QSFP28 and QSFP56 modules. The consistent single‐mode fiber plant can be reused, avoiding costly recabling. In this way, 100G IR4 acts as a bridge, delivering immediate gains while laying the groundwork for next‑generation speeds.
Conclusion
For high‑density ToR deployments supporting HPC and AI clusters, 100G IR4 transceivers deliver the ideal mix of bandwidth, reach, and efficiency. By consolidating ports, simplifying cabling, and reducing power consumption, IR4 enables compact, scalable, and cost‑effective edge switching. As workloads continue to demand more throughput in constrained spaces, 100G IR4 stands out as a future‑proof enabler of agile, high‑performance network design.
