400G QSFP-DD and OSFP Transceivers: Key Variants and Applications
As cloud-scale networks evolve, 400G transceivers have become a critical component in hyperscale data centers, AI clusters, and metro DCI links. This article provides a detailed comparison of 400G QSFP-DD and 400G OSFP modules, including SR8, DR4, DR4+, LR4, and explains their optimal use cases.
QSFP-DD vs OSFP: Understanding the Form Factors
| Feature | QSFP-DD | OSFP |
|---|---|---|
| Size | Compact (Hot-swappable) | Larger (Higher thermal tolerance) |
| Power Dissipation | Up to 12W | Up to 16W |
| Use Case | Broad switch compatibility | AI/ML intensive computing nodes |
| Interface Pins | 76 | 60 |
- QSFP-DD (Quad Small Form Factor Pluggable – Double Density): Widely used in Ethernet switches.
- OSFP (Octal Small Form Factor Pluggable): Preferred for NVIDIA AI/ML systems due to better cooling and power handling.
Key Variants of 400G Transceivers
1. 400G QSFP-DD SR8
- Standard: IEEE 802.3ck
- Interface: 8x50G PAM4 on MMF
- Reach: ≤100m over OM4
- Application: Intra-rack or short-reach interconnects
- Connector: MPO-16 or 2x MPO-12
- Power Budget: Low
2. 400G QSFP-DD DR4 / OSFP DR4
- Standard: 400GBASE-DR4 (IEEE)
- Interface: 4x100G PAM4
- Reach: 500m over SMF
- Connector: MPO-12
- Use Case: TOR to spine; leaf-to-leaf over single mode fiber
3. 400G QSFP-DD DR4+ / OSFP DR4+
- Enhanced Reach: 2km over SMF
- Same Electrical Interface as DR4
- Connector: MPO-12
- Application: Inter-building links or extended leaf-spine networks
4. 400G QSFP-DD LR4 / OSFP LR4
- Standard: 400GBASE-LR4 (4x100G CWDM)
- Modulation: PAM4
- Reach: 10km over duplex LC SMF
- Application: Metro DCI, long-haul links
Use Case Scenarios for 400G Modules
| Application Area | Recommended Module | Notes |
|---|---|---|
| Intra-Data Center (≤100m) | QSFP-DD SR8 / OSFP SR8 | Lowest latency, MMF |
| Leaf-Spine (≤500m) | QSFP-DD DR4 / OSFP DR4 | MPO-12 SMF |
| Metro DCI (≤2km) | DR4+ / LR4 | Tunable versions available |
| Long-Haul (10km) | LR4 | CWDM and FEC required |
Compatibility with AI & Hyperscale Networks
NVIDIA and Arista switches widely support both QSFP-DD and OSFP:
- NVIDIA Quantum-2 SN5600: Supports OSFP DR4/SR8
- NVIDIA CX7 NIC (Q112-400G-SR4): For SR4-based backbone
- Arista 7060X5 / 7060X6: Support both QSFP-DD SR8 and DR4
Conclusion
The selection of a 400G transceiver—whether QSFP-DD SR8, OSFP DR4, or LR4—depends on your use case, fiber infrastructure, and desired reach. High-performance networks require precision in both form factor and optical interface, especially when deployed in RoCE, AI/ML clusters, or metro DCI.
If you’re designing your next high-speed network or upgrading your interconnects, understanding these options will ensure optimal performance and future-proof scalability.
About Optech
Optech Technology Co. Ltd was founded in 2001 in Taipei, Taiwan. The company was created with a sole purpose, to provide a wide and high quality portfolio of optical products to a very demanding and fast evolving market.
To respond to the permanent increase of IP traffic, Optech portfolio is constantly growing. Since the beginning, the company has always been up to date with the latest innovations on the market. Today, we are proud to deliver a large selection of 25G SFP28, 40G QSFP+, 100G QSFP28, 200G QSFP56, 400G QSFP-DD, 800G QSFP-DD and OSFP optical transceivers and cables.
Optech has a large portfolio of products which include optical transceivers, direct attach cables, active optical cables, loopback transceivers, media converters and fiber patch cords.
Through its large selection of optical products, that have a range of data speed from 155 Mbps to 800 Gbps and reach distances up to 120km, Optech products are suitable for various industries such as telecom, data centers as well as public and private networks.
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For additional information about our 400G QSFP-DD and 400G OSFP Transceivers, or price inquiry, please contact us at sales@optech.com.tw
