The Road to 400G and 800G: Powering the AI Era

As artificial intelligence workloads explode and data center traffic surges, the optical networking industry is undergoing one of its most significant transformations in decades. The migration from 100G to 400G, 800G, and beyond is reshaping how we build and scale network infrastructure .

Where We Are Today
400G: The Mainstream Standard
400G has firmly established itself as the mainstream optical connectivity solution. Ciena reports strong and sustained demand for 400G wavelengths, with service providers and cloud operators worldwide adopting the technology to support growing bandwidth needs .

Key 400G applications include:
Data Center Interconnect (DCI): Connecting hyperscale data centers within metropolitan and regional distances (80-120 km)

Extended reach variants: 400G ZR+ supports transmission beyond 800 km with flexible bandwidth granularity 

800G: Rapid Acceleration
800G deployments are now beginning and expected to ramp rapidly in 2026 . According to Trendforce, global shipments of 800G and above optical modules are projected to reach nearly 63 million units in 2026—a staggering 2.6x growth .

The driving force? AI. GPU clusters distributed across multiple geographically dispersed data centers require high-speed optical interconnects. This emerging application is expected to push the market for high-speed interfaces to over one million units annually by 2030 .

The Technology Behind the Speed
Coherent Pluggables Revolution
The introduction of 800G ZR/ZR+ coherent pluggable modules represents a quantum leap in optical technology. These modules leverage advanced 3nm CMOS processes and deliver :

Dramatic power efficiency: 99% reduction in power per gigabit since 2000

Programmable performance: Dynamic rate adjustment from 800G down to 200G based on distance requirements

Multi-vendor interoperability: Seamless integration across different equipment providers

For example, Nokia's ICE-X 800G ZR+ modules can deliver 800G over 1,700+ km, 600G over 2,000+ km, and 400G over 3,000+ km—all in a compact QSFP-DD form factor .

CPO: The Next Frontier
Co-Packaged Optics (CPO) is emerging from the lab toward large-scale commercial deployment. By integrating optical engines directly with switch ASICs, CPO delivers :

50-70% power reduction
Signal loss reduction from 22dB to just 4dB

50%+ reduction in end-to-end latency
3.5x improvement in overall energy efficiency

NVIDIA launched Quantum-X InfiniBand switches with CPO in late 2025, with Spectrum-X Ethernet switches planned for late 2026. TSMC's COUPE platform is expected to enter mass production in the second half of 2026, with broad commercialization likely by 2027 .

Supply Challenges
The rapid transition has created supply bottlenecks, particularly for high-end lasers. EML and CW laser production requires multiple epitaxial growth steps and extended burn-in times, making capacity expansion difficult. While Lumentum and Coherent are expanding capacity by 40-100%, the gap between supply and demand remains significant, driving price increases .

Applications Across the Network
800G coherent pluggables have expanded far beyond their original DCI use case :
Metro Networks: Lowering cost per bit per kilometer
Backbone Connectivity: Direct integration into routers for high-capacity core links
AI Clusters: Connecting GPU clusters and storage architectures across data centers
Long-Haul DCI: Supporting 800G transmission over 1,700+ km

Looking Ahead: 1.6T and Beyond
The next milestone—1.6T—is already on the horizon. Early 1.6T products are entering production in 2026, driven by the insatiable bandwidth demands of AI workloads .

Key developments include:
Dual sub-carrier architecture for 1.6T ZR+ transmission

Advanced materials combining silicon photonics, indium phosphide, and thin-film lithium niobate

Sub-3nm CMOS processes for next-generation DSPs
OSFP, OSFP-XD, and QSFP-DD112 form factors 

Conclusion
The transition from 400G to 800G represents more than just a speed increase—it's a fundamental shift in network architecture driven by AI's insatiable appetite for bandwidth. With 800G becoming the standard for AI networks and 1.6T already on the horizon, the optical industry is entering an unprecedented "super cycle" of growth and innovation .

For network operators, the message is clear: the future is optical, and it's arriving faster than ever.