QSFP-DD400G·since 2017 (QSFP-DD MSA), 2020 (IEEE 802.3bs / cu)

QSFP-DD, Double-density 400G, backward-compatible cage, eight electrical lanes.

QSFP Double-Density (QSFP-DD MSA, IEEE 802.3ck). Eight electrical lanes in a slightly deeper QSFP envelope. Mechanically backward-compatible, QSFP-DD cages accept QSFP28 modules at 100G, which is the standard migration path from 100G to 400G data-center fabric. CMIS-based management.

Specifications

MSA references

QSFP-DD MSA rev 5.x (mechanical) · CMIS 4.0 / 5.0 (management)

Electrical interface

8 lanes × 26.5625 Gbaud PAM4 (50G per lane)

Power consumption

7 W – 14 W typical; up to 18 W for coherent ZR / ZR+ variants

Signalling

PAM4 with KP4 / RS-FEC

FEC

RS-FEC (544,514) required

Connector types

MPO-12 (DR4, FR4) · MPO-16 (DR8 / SR8) · LC duplex (LR4, ER4) · QSFP-DD DAC / AOC

Available SKUs

Part number	Spec	Wavelength	Fiber	Reach	Notes
`NAP-QSFPDD-SR8`	400GBASE-SR8	850 nm	MM OM4	70 m	MPO-16, 8 parallel
`NAP-QSFPDD-SR4.2`	400GBASE-SR4.2 (BiDi)	850/910 nm	MM OM4/5	100 m	MPO-12
`NAP-QSFPDD-DR4`	400GBASE-DR4	1310 nm	SM parallel	500 m	MPO-12, 4×100G PAM4
`NAP-QSFPDD-FR4`	400GBASE-FR4	LAN-WDM	SM	2 km	LC duplex
`NAP-QSFPDD-LR4`	400GBASE-LR4	LAN-WDM	SM	10 km	LC duplex
`NAP-QSFPDD-ER4`	400GBASE-ER4	LAN-WDM	SM	40 km	SOA-based
`NAP-QSFPDD-400ZR`	400G coherent ZR	C-band	SM	80–120 km	OIF 400ZR, DSP-based
`NAP-QSFPDD-400ZR-PLUS`	400G ZR+ (OpenZR+)	C-band	SM	500–1000 km+	Carrier-grade DCI
`NAP-QSFPDD-BREAKOUT`	400G → 4×100G DR	1310 nm	SM parallel	500 m	Standard fabric breakout

In production with

QSFP-DD modules are deployed across these platforms today. Full coding details are on the compatibility matrix.

Cisco Nexus 9300-GX/GX2, 9408, Silicon One platforms
Juniper QFX5130, QFX5220, QFX5240, MX10K
Arista 7060X5, 7280R3, 7500R3, 7800R3, 7060X6
Dell Z9332F, Z9432F, S5448F
Aruba CX 9300, 10000
NVIDIA Spectrum-4 (SN5000 series)

Operational notes

400ZR and 400ZR+ modules can draw 15–18 W. Verify chassis per-port power budget before populating every cage with coherent optics.

PAM4 sensitivity to dirty connectors is real, 400G installs warrant a fiber scope and a click-cleaner per port.

QSFP-DD cages accept QSFP28 modules at 100G, primary migration path from 100G to 400G is to deploy QSFP-DD-capable switches early and refresh optics later.

Recommended for

Modern data-center fabric (spine, leaf, ToR aggregation)
AI/ML training cluster east-west traffic (400G RoCE)
Hyperscale spine-spine links
Coherent DCI for metro and long-haul (400ZR / ZR+)

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