OSFP

What Is OSFP?

OSFP — Octal Small Form-factor Pluggable — is one of the two dominant high-speed pluggable form factors. Eight electrical lanes gives 400G at 50G per lane, 800G at 100G per lane, and 1.6T at 200G per lane in the OSFP224 variant.

It was specified with a slightly larger body than QSFP-DD, and that extra volume is the whole argument for it: more room for heat spreading, and a thermal path that can carry the 20 to 30 watts that 800G and 1.6T optics dissipate.

RHS and Flat-Top, and Why It Matters

Two mechanical variants matter in practice. OSFP with an integrated riding heat sink — RHS — puts the thermal interface on the module itself. Flat-top OSFP, sometimes called IHS, relies on a heat sink in the cage, which is what liquid-cooled and some high-density switch designs want.

They are not interchangeable. A flat-top module in a cage expecting a riding heat sink has no thermal path and will run hot — and the symptom is a module that works in the lab and throttles or errors in a full rack. Tell your supplier the switch model, not just the form factor.

What It Does Not Do

OSFP is not mechanically backward-compatible with QSFP or QSFP28. Where that matters, an OSFP-to-QSFP adapter exists and works, at the cost of a slot's worth of space and some thermal margin.

For an operator with a large installed base of 100G optics, that is a genuine disadvantage and is the main reason QSFP-DD still dominates general-purpose data centre switching.

Where You Meet It

OSFP dominates in AI and HPC fabrics, particularly NVIDIA InfiniBand and Spectrum-based Ethernet clusters, largely because of the thermal headroom. Check what a full switch does to your rack budget in the power and thermal calculator before finalising a design.

See our OSFP transceiver range across 400G, 800G and 1.6T.

Related Terms

QSFP-DD, OSFP-XD, QSFP112, and the head-to-head comparison.