The Linear Pluggable Optics Multi-Source Agreement (LPO MSA) Group unveiled the 400G-FR4-LPO specification during ECOC 2025 in Copenhagen. The new standard defines a 100 Gb/s per lane single-mode optical data transmission format using four wavelength-division multiplexed (WDM) lanes, extending linear pluggable optics to 400 Gigabit Ethernet connectivity.
The 400G-FR4-LPO specification supports reaches of at least 500 meters over a pair of single-mode fibers, complementing the 100G-DR-LPO specification released in March 2025. Together, these standards provide data center operators with options for linear pluggable solutions across both DR and FR4 links. The LPO MSA, which includes more than 50 networking, semiconductor, and optics companies, aims to drive down power consumption, cost, and latency for high-speed optical interconnects, particularly in AI/ML workloads.
The specification builds on IEEE 802.3, OIF, and other standards to ensure interoperability across components, modules, and systems operating at 100 Gb/s per lane. The group also confirmed that it has initiated work on 200 Gb/s per lane linear implementations, with plans to collaborate with OIF and IEEE to extend the benefits of LPO technology to the next generation of interconnects.
• Defines 400G-FR4-LPO single-mode optical transmission at 100 Gb/s per lane
• Supports at least 500 m reach over SMF with four WDM lanes
• Complements 100G-DR-LPO released March 2025
• Targets reduced power, cost, and latency for high-speed AI/ML data center links
• Work underway on 200 Gb/s per lane linear specifications
“We are pleased to be able to scale the 100G/lane SMF LPO solution to include FR4 links, which provides the industry expanded LPO connectivity options,” said Mark Nowell, LPO MSA Chair. Andreas Bechtolsheim, LPO MSA Co-Chair, added: “This additional specification gives datacenter operators deployment flexibility between two major single mode link types leveraging LPO.”
🌐 Analysis: The release of a second LPO specification shows steady progress by the consortium, but questions remain about real-world adoption. DSP-based modules still dominate volume deployments due to their maturity and proven performance, while LPO modules have only begun to see early trials. By expanding beyond 100G-DR to 400G-FR4, the group is broadening the applicability of linear optics and making the ecosystem more attractive to hyperscalers. If major switch and NIC vendors embrace the FR4 option, this could accelerate traction, though much will depend on interoperability testing and demonstrated power savings at scale. The parallel work on 200G per lane LPO signals that the group intends to keep pace with 1.6 Tbps and beyond architectures.
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