CodingBox Documentation

OSFP

Octal Small Form-factor Pluggable (OSFP) is the other eight-lane 400G/800G form factor. It is deliberately larger than QSFP-DD and carries an integrated heat sink, so it can dissipate more power — the trade-off that makes it the preferred choice for the hottest, longest-reach and highest-rate modules, including InfiniBand NDR and the path to 1.6T.

Key facts

Lanes × rate8 × 50G (PAM4) → 400G; 8 × 100G (PAM4) → 800G; OSFP-XD: 16 lanes → 1.6T
Total400G / 800G / 1.6T
ConnectorMPO-12/MPO-16 (DR4/DR8/SR8), LC duplex (FR4/LR4), dual LC/MPO (2×400G), DAC/AOC
Supply3.3 V; power classes well above QSFP-DD thanks to the integrated heat sink
Applications400GbE/800GbE spines and AI fabrics, InfiniBand NDR (400G), 2×400G "twin-port" modules

Specifications

  • OSFP MSA specification — mechanical (including the integrated heat sink),

electrical and thermal definition; revisions cover 400G, 800G and OSFP-XD.

  • OSFP-RHS ("riding heat sink") — a variant with a host-side heat sink to fit

lower-profile faceplates.

  • Management: CMIS — see CMIS.

Management interface

OSFP is CMIS-only, sharing the same management model as QSFP-DD: module state machine, per-lane data paths, application selection, banked pages and the CDB command interface. This means an OSFP and a QSFP-DD module of the same PMD look identical to management software; only the mechanical and thermal envelope differs. Codes are from SFF-8024.

Compatibility notes

  • Not mechanically compatible with QSFP or QSFP-DD ports — an OSFP module needs an

OSFP cage (adapters exist to run QSFP-family modules in an OSFP port).

  • Common in InfiniBand NDR switching and in 800G AI fabrics; "twin-port" OSFP modules

present two independent 400G ports from one module.

In CodingBox

CodingBox reads OSFP with the CMIS decoder — the top end of its "GBIC to OSFP" range. Module state, identity, applications and per-lane DDM are available on the Check transceiver, EEPROM editor and DDM screens; bring-up problems are covered in CMIS issues.