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

QSFP-DD: 400G in a double-density QSFP envelope — eight lanes of 50G PAM4.

QSFP Double-Density (QSFP-DD MSA, IEEE 802.3bs / 802.3cd). Eight electrical lanes at 50 Gbps PAM4 in a slightly deeper QSFP envelope. Mechanically backward-compatible — QSFP-DD cages accept QSFP28 modules at 100G, which made QSFP-DD the dominant migration path from 100G to 400G data-center fabric during 2020–2024. Still widely deployed and supported across major switch vendors. CMIS-based management. NetAPI sells both QSFP-DD and QSFP112 for 400G — pick by host switch.

Specifications

MSA references

QSFP-DD MSA rev 5.x (mechanical) · CMIS 4.0 / 5.0 (management) · IEEE 802.3bs / 802.3cd

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 / OM5	100 m	MPO-12
`NAP-QSFPDD-DR4`	400GBASE-DR4	1310 nm	SM parallel	500 m	MPO-12
`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
`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

QSFP-DD cages accept QSFP28 modules at 100G — the original 100G → 400G migration path. New QSFP112-only switches don't have this benefit.

Eight lanes at 50G NRZ mean tighter per-lane signalling margins than QSFP112's four lanes at 100G PAM4 — slightly more forgiving on host SerDes, slightly more silicon on the module side.

QSFP-DD and QSFP112 are not mechanically interchangeable. Confirm cage type before ordering — modern data-center switches usually expose both, but not every line card does.

QSFP-DD800 is the 8-lane, 100G-per-lane evolution of this form factor for 400G or 800G; see the OSFP / QSFP-DD800 alternatives note on the OSFP page.

Recommended for

Data-center fabric on existing QSFP-DD-capable switches
Sites migrating from 100G QSFP28 spines (cage-compatible)
Multi-vendor procurement where QSFP-DD is the lowest-common-denominator 400G cage
Storage and HPC fabric where 8-lane signalling tolerances are preferred

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