Solutions & Applications
Telecom Network Sync · 5G Infrastructure · Data Center Connectivity · Optical Networks · Critical Networks
50%Fewer Leaf Ports
18 kWPower Saved
100 GbpsPer Lane PAM4
1. The Challenge
Training a single frontier LLM today demands 20,000–50,000 GPUs running nonstop for months. At 400G per port, the all-reduce traffic alone saturates fabric bandwidth long before the silicon does.
Port Explosion
A 10K-GPU cluster at 400G demands 1,024+ leaf ports and 64 spine switches. Doubling to 20K GPUs doubles the pain.
Power Ceiling
Each 400G-DR4 module draws ~10W. At 2,000+ modules, the interconnect alone consumes 20 kW before counting switch silicon.
Cable Density
MPO-12/APC trunk cables eat rack space and block airflow. Managing 512+ fiber pairs per row is a logistics headache.
End-to-End Latency
Every extra O-E-O conversion adds nanoseconds that compound across thousands of all-reduce rounds.
Root Cause: The bottleneck is not the GPU or the switch ASIC — it is the optical interconnect. Moving from 400G to 800G optics cuts port count in half, shrinks switch radix, and trims per-bit power by 15–25%.
2. Solution Architecture
A three-tier optical fabric from intra-rack GPU links to inter-building cluster aggregation:
| Tier | Scope | Product | Form Factor | Reach |
|---|---|---|---|---|
| Tier 1 | GPU ↔ ToR Switch (0–100 m) | 800G QSFP-DD SR8 + 800G AOC | QSFP-DD | 100 m / 3–30 m |
| Tier 2 | Leaf ↔ Spine (0–500 m) | 800G QSFP-DD DR8 / FR4 | QSFP-DD | 500 m / 2 km SMF |
| Tier 3 | Cluster ↔ Inference / DCI (2–500+ km) | 800G QSFP-DD ZR+ + DWDM MUX + EDFA | QSFP-DD / 1RU | 500–2,000+ km |
3. Key Benefits
50% fewer leaf ports vs. equivalent 400G deployment
18 kW interconnect power saved per 10K-GPU cluster
2× bandwidth density per RU vs. 400G-DR4
<1>per optical link (in-cabinet)
4. Why Apex Optics
| Capability | What It Means |
|---|---|
| Multi-vendor interoperability | Tested with Broadcom Tomahawk 5, Cisco Silicon One, and NVIDIA Spectrum-4 switches — no lock-in. |
| Pre-configured DWDM mux | 40-channel MUX/DEMUX ships pre-wired on LGX panels — rack, plug, and light within hours. |
| End-to-end IL/RL testing | Every transceiver ships with insertion loss and return loss trace data — no guesswork at commissioning. |
| Hot-plug inventory | All QSFP-DD modules ship from stock; same-day dispatch for clusters up to 2,048 ports. |
| Firmware consistency | Single CMIS revision across the entire 800G fleet — no intermix bugs. |
5. Deployment Scenario: 10,240-GPU Training Pod
A cloud provider building a new AI training region with 10,240 H100-class GPUs across 1,280 nodes:
| Parameter | 400G Baseline | 800G Apex Solution | Delta |
|---|---|---|---|
| Leaf ports required | 2,048 | 1,024 | −50% |
| Spine switches | 128 | 64 | −50% |
| Optical transceivers | 4,096 × 400G-DR4 | 2,048 × 800G-DR8 | −50% |
| Interconnect power | ~41 kW | ~23 kW | −18 kW |
| Fiber strands (leaf–spine) | 4,096 MPO-12 | 1,024 SMF duplex | −75% |
| Rack space (spine layer) | 16 racks | 8 racks | −8 racks |
Bottom Line: Moving to an 800G optical fabric saves 8 racks, 18 kW, and 2,048 optical ports per 10K-GPU pod — while cutting fiber count by 75%. The freed power budget goes directly into GPU density.
Designing an AI cluster optical fabric?
Our solutions engineers will model your topology, recommend a product matrix, and provide a full BOM with lead times — typically within 48 hours.
Email: Info@apexallinone.com | WhatsApp/Phone: +852 9821 3834
