400ZR, 800ZR, OpenZR+: What Are They and Which DCI Network Needs Them?

Your network between data centres is generating more and more traffic, and the cost of every gigabit matters. ZR standards are the technology that allowed companies to cut out external transponders and connect coherent optics directly to a router port. It sounds technical, but the effects are purely business: less equipment, a lower energy bill, and more freedom when choosing partners.

Why DCI Got More Expensive and How ZR Fixed It

Traditional connections between data centres required dedicated transponders, which translated into additional rack space, more electricity, extra pairs of grey modules, and lock-in to a single vendor. Changing vendors meant replacing the entire stack — hardware and software together. You were tied to one vendor for as long as your infrastructure ran.

OIF (Optical Internetworking Forum) decided to change that. In 2016 it initiated work on the 400ZR standard — an interoperable coherent module in a pluggable form factor (QSFP-DD or OSFP) that you slide directly into a router or switch port, like a USB drive into a laptop. The standard was deployed in 2020 and has since become the most widely adopted coherent standard in the history of the industry.

In 2024, OIF approved 800ZR — the next generation, doubling throughput to 800 Gb/s while preserving the same plug-and-play philosophy and full multi-vendor interoperability.

Three Standards - One Line About Each

400ZR

400 Gb/s — range up to 120 km — approved 2020

Full multi-vendor interoperability. Today the most widely deployed coherent standard in history. Millions of modules working in networks around the world.

Most widely deployed

800ZR

800 Gb/s — up to 120 km DCI or up to 1,000 km in ZR+ mode

Approved by OIF in October 2024. Mass rollout from 2026, projected growth of 145% CAGR to 2029 per Cignal AI. At OFC 2026 — 40 companies confirmed interoperability.

145% CAGR growth to 2029

OpenZR+

100–400 Gb/s adaptive — range up to 2,000+ km

A flexible standard with adaptive modulation. Used in metro and backbone networks where longer range matters more than maximum throughput per module.

Metro and backbone

What Is Behind the 10x Growth in Interest in 800ZR?

Dell’Oro Group recorded a 10x year-over-year increase in interest in ZR+ modules (2025 vs. 2024). The reason is concrete: hyperscalers are building distributed GPU clusters spanning 3–5 locations within a 50–500 km radius. Every such link needs 400G or 800G coherent — no other format offers this combination of throughput, range, and deployment simplicity.

At OFC 2026 in March in Los Angeles, 40 companies demonstrated live multi-vendor interoperability of 800ZR. This signals that the production ecosystem is ready for mass deployments and the risk of single-vendor lock-in has ceased to exist.

Cignal AI projections indicate that after 2026, network bandwidth growth will be dominated by pluggables. Coherent modules 800ZR and 1600ZR will together exceed 50% of all coherent modules shipped by 2030. Hyperscalers today spend twice as much on coherent modules as all telecommunications operators combined.