Migrating to 400G: Technologies and Strategy

Migration to 400G (400 Gbps per port) is becoming essential for modern data centers due to the surge in AI/ML traffic (DGX H100 with 8×400G NIC), spine-leaf architectures with more than 50 racks, and cloud provider requirements. QSFP-DD replaces QSFP28. This 2026 guide covers 400G migration equipment, transceivers, fiber, and budgets.

Why migrate to 400G?

• AI/ML: NVIDIA DGX H100 = 8×400G Ethernet or InfiniBand
• Spine-leaf: 400G links between spine switches reduce oversubscription
• Data center interconnect (DCI): 400G ZR optics for metro networks
• Hyperscale: AWS, Google, and Microsoft are moving from 400G to 800G
• Cost efficiency: 1×400G costs less overall than 4×100G and requires fewer ports

QSFP-DD form factor

• QSFP-DD (Double Density): 8 lanes × 50G or 8×56G
• Backward-compatible with QSFP28 slots: can accommodate a 100G module
• Power consumption: typically 10-20W (vs 3.5W for QSFP28)
• Cooling: dense designs require careful thermal management
• OSFP alternative: a competing format adopted by NVIDIA but less widely used in networking

400G technologies

Serial 100G PAM4

• 400G-DR4: 4×100G PAM4 lanes, MPO-12 fiber
• 400G-FR4: 4×100G WDM, duplex single-mode fiber
• 400G-LR4: 10 km, duplex single-mode fiber
• 400G-ZR: 80-120 km, coherent, DWDM
• 400G-ZR+: >120 km, coherent optics

Breakout options

• 1× QSFP-DD 400G → 4× QSFP28 100G (MPO breakout)
• 1× QSFP-DD 400G → 8× SFP56 50G
• 1× QSFP-DD 400G → 4× 100G FR1 duplex (400G-FR4 breakout)

400G switches in 2026

• Cisco Nexus 9364D-GX2A: 64×400G QSFP-DD, 25.6 Tbps — €180,000 excl. VAT
• Juniper QFX5130-32CD: 32×400G — €65,000 excl. VAT
• Arista 7280CR3K-32D4: 32×400G + 4×400G ZR — €95,000 excl. VAT
• Nokia 7250 IXR-18: telecom-grade 400G
• Cisco Catalyst 9500: up to 4×400G through uplink modules

400G transceivers on the market in 2026

• QSFP-DD-400G-SR8: multimode, 100m — €3,500 excl. VAT (new Cisco) vs €1,500 (OPTINOC-compatible)
• QSFP-DD-400G-DR4: single-mode, 500m — €5,000 excl. VAT vs €2,200
• QSFP-DD-400G-FR4: single-mode, 2 km — €6,500 excl. VAT vs €2,900
• QSFP-DD-400G-LR4: single-mode, 10 km — €9,900 excl. VAT vs €4,500
• QSFP-DD-400G-ZR: coherent, 80 km — €25,000 excl. VAT

Fiber and connectivity

• OM4 multimode: supports 400G-SR8 up to 100m
• OM5 multimode: recommended for 400G SWDM, 400m
• OS2 single-mode: 400G-FR4/LR4/ZR
• MPO-16: new connector for 8 parallel lanes
• MPO-12: legacy connector, sometimes usable with an adapter

400G migration budget

Spine-leaf fabric upgrade (medium-sized DC)

• 4× Cisco Nexus 9364D-GX2A 400G spine switches: 4× €180,000 = €720,000 excl. VAT
• 64× 400G-DR4 transceivers: 64× €2,200 (OPTINOC) = €140,800 excl. VAT
• Existing single-mode MPO fiber: reusable
• Total spine upgrade: approximately €870,000 excl. VAT

ROI compared with remaining on 100G

• Equivalent 100G capacity: 16× Nexus 93360YC-FX2 spine switches = 16× €90,000 = €1,440,000 excl. VAT
• 400G savings: 40% lower cost + 70% fewer ports + 50% lower power consumption
• Typical ROI: 18-24 months

Order from OPTINOC

Turnkey 400G migration: Cisco Nexus, Juniper QFX, and Arista 7280 switches plus OPTINOC-compatible QSFP-DD transceivers (50% to 60% less than manufacturer pricing, with guaranteed EEPROM coding). DC migration quote within 48 hours.