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In AI/ML clusters, hyperscale data centers, and carrier-grade backbones, the Optical Transceiver Module is where bandwidth, thermals, and interoperability collide.
Building on the same framework as your 40G/200G articles, this deep-dive introduces the NS brand (owned by Network-Switch.com) 400 Gbps Module lineup: QSFPDD-400G-SR8, QSFPDD-400G-DR4-S, QSFPDD-400G-FR4, OSFP-400G-SR4-FLT, OSFP-400G-DR4-FNT, QSFP112-400G-DR4, and QSFP112-400G-SR4.
Each Fiber Optic Transceiver Module is engineered for High Speed switching and routing and is available as Cisco Compatible Modules and Nvidia Compatible Modules with multi-vendor coding and CMIS-based management for smooth operation alongside Huawei and other mainstream platforms.
Product Overview
At 400G, three form factors dominate:
- QSFP-DD (Quad Small Form-factor Pluggable—Double Density): 8 electrical lanes at 50G PAM4 (400GAUI-8). Used by SR8, DR4-S, FR4.
- QSFP112: next-gen QSFP with four 112G PAM4 lanes (400GAUI-4), delivering 400G in a compact cage with different thermal trade-offs.
- OSFP: physically larger with more heatsinking headroom; available in Finned Top (FNT) and Flat Top (FLT) mechanicals to match switch airflow and adjacent port spacing. Optics behavior is the same—only the top heatsink differs in height/shape.
Across this NS portfolio you’ll find short-reach MMF (SR8/SR4), parallel SMF for 500 m leaf–spine (DR4/DR4-S), and duplex SMF for 2 km links (FR4). These building blocks map to a majority of 400G architectures without locking you to a single vendor OS.
Result: fewer SKUs in sparing, faster roll-outs, and consistent visibility via DDM/DOM.
Hardware Specifications
| Model | Wavelength | Max Reach | Connector | Lane Architecture | Typical Power (max) |
| QSFPDD-400G-SR8 | 850 nm | 70 m (OM3) / 100 m (OM4) | MPO-16 | 8×50G PAM4 (SR8) | up to ~10 W (vendor-dep.) |
| QSFPDD-400G-DR4-S | 1310 nm | 500 m | MPO-12 | 4×100G PAM4 (parallel) | up to ~12 W (vendor-dep.) |
| QSFPDD-400G-FR4 | 4×CWDM (≈1271/1291/1311/1331) | 2 km | LC duplex | 4×100G PAM4 (wavelength mux) | up to ~12 W (vendor-dep.) |
| OSFP-400G-SR4-FLT | 850 nm | 30 m (OM3) / 50 m (OM4) | MPO-12 | 4×100G PAM4 (SR4) | vendor-dep.; FLT top for tight spaces |
| OSFP-400G-DR4-FNT | 1310 nm | 500 m | MPO-12 | 4×100G PAM4 (DR4) | FNT = integrated finned heatsink for higher cooling headroom |
| QSFP112-400G-DR4 | 1310 nm | 500 m | MPO-12 | 4×100G PAM4 (DR4) | vendor-dep. (compact thermals) |
| QSFP112-400G-SR4 | 850 nm | 70 m (OM3) / 100 m (OM4) | MPO-12 | 4×100G PAM4 (SR4) | vendor-dep. (compact thermals) |
Notes & what the specs mean:
- SR8 (QSFP-DD) runs eight 50G PAM4 lanes over 16-fiber ribbon (MPO-16). It’s the simplest “drop-in” for high-density MMF plants up to 100 m on OM4.
- DR4 / DR4-S use four fibers each direction at 1310 nm with 100G PAM4 per lane for 500 m over SMF. The “-S” SKU is widely used for easy 4×100G breakout to DR/FR/LR on the far side, verified on Cisco’s QDD-400G-DR4-S datasheet.
- FR4 places four 100G lanes onto four CWDM wavelengths around 1310 nm for 2 km on duplex SMF—clean cabling, simple patching, and standard host FEC.
- OSFP SR4 (FLT) provides Flat Top thermals for rows with tighter vertical clearance; OSFP DR4 (FNT) offers Finned Top for higher heat dissipation—optics function is the same, the heatsink is not.
- QSFP112 brings 400G on four electrical lanes (400GAUI-4) into the familiar QSFP faceplate—great where thermal budgets allow and operators prefer QSFP cages over DD/OSFP.
Compatibility & Interoperability
NS 400G optics align with IEEE 802.3bs/cu PMDs and the relevant QSFP-DD / QSFP112 / OSFP MSAs with CMIS management.
In practice, that means you can deploy them as Cisco Compatible Modules on Nexus/Catalyst data center gear, and as Nvidia Compatible Modules on Spectrum-based Ethernet or ConnectX NICs; they also integrate with Huawei/other mainstream vendors that support these 400G PMDs. For example:
- QSFP-DD 400G-FR4 is defined for 2 km duplex SMF with 4 CWDM λ and host FEC per IEEE 802.3cu—exactly how Cisco QDD-400G-FR4-S behaves.
- QSFP-DD 400G-SR8 uses MPO-16 and reaches 100 m on OM4, compliant with 400GAUI-8 electrical I/O.
- QSFP-DD 400G-DR4-S supports 500 m, MPO-12, and 4×100G breakout to DR/FR/LR optics at the far side—standardized behavior seen in Cisco’s datasheet set.
- QSFP112 400G-DR4/SR4 modules run over MPO-12 (SMF or MMF) and are documented by multiple vendors as 500 m (DR4) and 70/100 m (OM3/OM4 for SR4).
- OSFP finned vs flat-top is a mechanical/thermal choice only; both interoperate identically when the PMD matches (SR4 vs DR4).
NS Modules vs. OEM Modules vs. Other 3rd-Party Options
| Feature | NS Brand (QSFP-DD / QSFP112 / OSFP) | OEM (e.g., Cisco/Nvidia) | Other 3rd-Party |
| Multi-Vendor Coding | Cisco/Nvidia/Huawei, etc. | Vendor-locked SKUs | Varies |
| Standards Compliance | IEEE 802.3bs/cu, MSA, CMIS | Same | Varies |
| Variants Covered | SR8, DR4-S, FR4, SR4(FLT), DR4(FNT), QSFP112 SR4/DR4 | Full | Often partial |
| FEC/DOM/CMIS | Full | Full | Varies |
| Thermals | FLT/FNT choices in OSFP; QSFP112/QSFP-DD standard cages | Designed per platform | Mixed |
| Commercials | Simplified sparing & pricing | Premium contracts | Inconsistent |
Bottom line: NS targets OEM-class performance and telemetry with genuine multi-vendor operation—ideal when your fabric spans QSFP-DD, QSFP112, and OSFP cages across different switch families.
Deployment Scenarios & Use Cases
Data-Center Spine/Leaf
- QSFPDD-400G-SR8: short-reach leaf↔spine over OM4 trunks up to 100 m; ideal where 16-fiber ribbons are already pulled.
- QSFP112-400G-SR4: MPO-12 SR4 for operators standardizing on QSFP112 cages and 4-lane electrical interfaces (400GAUI-4).
AI/ML Fabrics & HPC
- QSFP112-400G-DR4 and OSFP-400G-DR4-FNT: 1310-nm parallel SMF to 500 m—a sweet spot for low-loss leaf-to-spine across halls or nearby rooms; OSFP FNT helps if your chassis runs hotter under AI loads.
Campus Backbone & Inter-Building
- QSFPDD-400G-FR4: duplex SMF to 2 km with clean cabling and easy patch-panel management; host RS-FEC as per the standard.
Migration & Breakout
- QSFPDD-400G-DR4-S: run 400G today or break out to 4×100G DR/FR/LR domains during phased migrations. This is a common move in brownfield builds and is explicitly supported on leading platforms.
Mixed Thermal Environments
- OSFP-400G-SR4-FLT where vertical space is tight (flat top), and OSFP-400G-DR4-FNT where airflow is robust (finned top). Same optics, different heatsinks.
Product Management
Installation & Diagnostics
Although NS modules are “generic,” they expose the same control/telemetry as OEM optics:
- DDM/DOM via CMIS (I²C): temperature, Vcc, TX/RX power, bias currents, lane status.
- Hot-swap on compliant cages without disturbing neighbor ports.
- CLI checks (typical): Cisco NX-OS/IOS-XE: show interface transceiver details Nvidia Cumulus/Linux: ethtool -m (where DOM is exposed) Huawei VRP: display transceiver interface
- Cisco NX-OS/IOS-XE: show interface transceiver details
- Nvidia Cumulus/Linux: ethtool -m (where DOM is exposed)
- Huawei VRP: display transceiver interface
About FEC: 400G PAM4 links require host FEC, that’s how error performance and reach are standardized. Ensure line cards/NICs have RS-FEC enabled for SR8/DR4/FR4 per IEEE specs.
Link sanity tips:
- On SR8/SR4, verify MPO polarity and fiber mapping; asymmetrical lane power usually flags a polarity/cable map issue.
- On DR4/FR4, check each lane’s RX power in DOM and confirm host FEC is active before chasing BER.
Technical Support & After-Sales Service
Network-Switch.com backs the NS line with:
- 24/7 pre-/post-sales engineering (PMD selection, link budgets, DOM interpretation)
- Rapid RMA with advance replacement where available
- EEPROM coding updates for evolving switch OS checks and tighter vendor optics policies
- Ongoing regression tests to preserve “Cisco Compatible Modules / Nvidia Compatible Modules” behavior over time
FAQs
Q1: QSFP-DD vs QSFP112 vs OSFP—how should I choose?
- QSFP-DD: common on fixed switches and line cards; 8 electrical lanes @ 50G PAM4 (SR8/DR4/FR4). Great ecosystem, broad availability.
- QSFP112: 4 lanes @ 112G PAM4 (400GAUI-4) in a QSFP cage—denser faceplates where thermals allow.
- OSFP: more thermal headroom; pick Finned Top for higher cooling, Flat Top for tight clearances—optics performance is identical.
Q2: What fibers and connectors do I need?
- SR8: OM3/OM4 with MPO-16; 100 m on OM4 typical.
- SR4 (OSFP/QSFP112): OM3/OM4 with MPO-12; up to 50–100 m depending on vendor and fiber grade.
- DR4/DR4-S: SMF with MPO-12; 500 m reach.
- FR4: SMF with LC duplex; 2 km reach.
Q3: Can DR4-S break out to 4×100G?
Yes. QDD-400G-DR4-S explicitly supports 4×100G breakout to DR/FR/LR on the far side and is documented by Cisco and multiple vendors.
Q4: What about power?
Expect ~8–12 W max depending on PMD/form factor and ambient temperature: SR8 often around ≤10 W, FR4 around ≤12 W, DR4 ~≤10–12 W (device-dependent). Validate your line-card per-port budget.
Q5: Are NS modules plug-and-play across Cisco, Nvidia, Huawei?
Yes—coding/CMIS profiles follow the MSAs and IEEE PMDs. Real-world datasheets confirm behaviors such as FR4 2 km duplex SMF and DR4-S 500 m with 4×100G breakout on Cisco platforms; NS aligns with those same standards.
Conclusion
The NS 400G lineup gives you precise tools for every topology:
- QSFPDD-400G-SR8 for shortest MMF trunks with MPO-16
- QSFPDD-400G-DR4-S for 500 m parallel SMF and 4×100G breakout
- QSFPDD-400G-FR4 for neat 2 km duplex SMF runs
- OSFP-400G-SR4-FLT/OSFP-400G-DR4-FNT to match your thermal envelope without changing optics behavior
- QSFP112-400G-SR4/DR4 where four-lane 112G PAM4 cages are preferred
Because the NS Fiber Optic Transceiver Module family adheres to IEEE/MSA and CMIS conventions, you can deploy QSFP-DD, QSFP112, and OSFP across mixed vendors as true Cisco Compatible Modules and Nvidia Compatible Modules, avoiding lock-in while maintaining High Speed stability. Standardize on NS to streamline sparing, simplify migrations, and keep your 400G build clean—today and as you scale.
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