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By Topnet Engineering Team | Updated July 2026
✓ In Stock | Free Sample Available - see our sample policy | Volume & Tender Pricing - sales@topnetsystem.com
SFP, SFP+, SFP28, QSFP+, QSFP28, QSFP56, QSFP-DD, QSFP112, OSFP... the alphabet soup of pluggable form factors confuses even experienced buyers. Each generation is defined by two numbers - lanes and speed per lane - and once you see that pattern, every module name decodes itself. This reference explains the whole family tree and which cages accept which modules.
| Form factor | Lanes x Speed | Total | Era / typical role |
| SFP | 1 x 1.25G | 1G | Access, FTTx, legacy enterprise - see 1-6G SFP |
| SFP+ | 1 x 10G | 10G | The most shipped optic ever; servers, uplinks |
| SFP28 | 1 x 25G | 25G | Server access standard - see 25G SFP28 |
| QSFP+ | 4 x 10G | 40G | First quad generation; breakout to 4x10G |
| QSFP28 | 4 x 25G | 100G | Aggregation workhorse - see 100G QSFP28 |
| QSFP56 | 4 x 50G PAM4 | 200G | HPC and transitional fabrics |
| QSFP-DD | 8 x 50G PAM4 | 400G | Double-density row; backward compatible cage - see 400G QSFP-DD |
| QSFP112 | 4 x 100G PAM4 | 400G | Newer 4-lane 400G; also 8x100G = 800G variants |
| OSFP | 8 x 100G PAM4 | 800G | AI cluster standard - see 800G OSFP |
| OSFP224 | 8 x 200G PAM4 | 1.6T | Emerging XDR-class fabrics |
The SFP lineage (SFP to SFP+ to SFP28) shares one cage size - newer ports accept older modules, which run at their native speed. The QSFP lineage does the same: a QSFP-DD port accepts QSFP+/QSFP28/QSFP56 modules. OSFP is the exception - it is a different, larger cage and accepts only OSFP modules (OSFP-RHS variants exist for specific platforms). This is why mixed 400G estates must track port types per device: a QSFP-DD optic will not enter an OSFP cage, full stop.
QSFP-DD won Ethernet switching on density and cage compatibility; OSFP won AI clusters on thermal headroom (integrated finned heatsinks up to ~18W and beyond). Neither is "better" - your platform decides. Our 800G selection guide and 400G guide cover the choice in depth per speed tier.
Yes - it runs at 10G. The reverse (SFP28 in an SFP+ port) also usually works at 10G if the module supports dual-rate.
It is the electrical lane speed: QSFP28 = 4 lanes of 28Gbps-class (25G data), QSFP56 = 4x50G PAM4, QSFP112 = 4x100G PAM4. DD means double density - eight lanes instead of four.
For existing 40G estates, yes - modules and breakout cables remain cost-effective for extending life. For new builds, 25G/100G is the better baseline.
No - OSFP cages accept only OSFP modules. Plan adapters or separate optics inventory when your estate mixes OSFP switches with QSFP-DD NICs.
A common blueprint: SFP28 25G at server access, QSFP28/QSFP112 at leaf, QSFP-DD or OSFP 400G/800G at spine, with DR4-class optics and MPO Type-B cabling as the structured layer. Ask our engineers for a free design review.
Topnet System (ISO certified since 2008) manufactures every generation in this table - from 1G SFP through 100G QSFP28 to 800G OSFP/QSFP112 and 1.6T-ready designs - with samples available under our Free Sample & Testing Policy. Email sales@topnetsystem.com for cross-reference help on any legacy or current part number.