Transceiver Form Factors
Common optical transceiver form factors and their capabilities.
Transceivers come in standardized form factors that tie together speed, port density, and media. SFP carries up to 1G, SFP+ and XFP 10G, SFP28 25G, QSFP+ 40G, QSFP28 100G, and QSFP-DD up to 400G.
The table below shows each form factor with its maximum speed, supported media, reach, and connector type, the reference you need when ordering optics or planning switch port capacity.
| Form Factor | Max Speed | Media | Max Distance | Connector |
|---|---|---|---|---|
| SFP (1G) | 1 Gbps | Copper / MMF / SMF | 100 m – 120 km | LC / RJ-45 |
| SFP+ (10G) | 10 Gbps | Copper / MMF / SMF | 30 m – 80 km | LC / RJ-45 |
| SFP28 (25G) | 25 Gbps | MMF / SMF | 100 m – 10 km | LC |
| QSFP+ (40G) | 40 Gbps | MMF / SMF | 100 m – 40 km | MPO / LC |
| QSFP28 (100G) | 100 Gbps | MMF / SMF | 100 m – 80 km | MPO / LC |
| QSFP-DD (400G) | 400 Gbps | MMF / SMF | 100 m – 40 km | MPO / LC / CS |
| CFP2 | 100 Gbps | SMF | 10 km – 80 km | LC |
| XFP | 10 Gbps | MMF / SMF | 300 m – 80 km | LC |
| CXP | 100 Gbps | MMF | 100 m | MPO |
Frequently Asked Questions
What is an SFP port?
An SFP port is a hot-swappable slot that accepts a small transceiver module instead of a fixed connector. The same port can carry fiber or copper depending on the module you insert, and its speed depends on the module type: SFP for 1G, SFP+ for 10G, and SFP28 for 25G.
What is the difference between SFP, SFP+ and SFP28?
All three use the same physical slot, but they run at different speeds: SFP carries up to 1G, SFP+ up to 10G, and SFP28 up to 25G. A 10G SFP+ module usually needs an SFP+ port, so check the switch specification before mixing them.
Can I put a 10G SFP+ module in a 1G SFP port?
Usually not. The host port must support the speed and protocol of the module, and most 1G SFP ports will not run a 10G SFP+ optic. Where a port supports multiple rates the module and port negotiate it, but the safe assumption is that the port sets the ceiling.
What is a QSFP28 port used for?
A QSFP28 port carries 100G, usually as four 25G lanes. That lets you run a single 100G uplink, or break the port out into four separate 25G links with a breakout cable, which is why it is common on spine switches and high-density servers.
Do I need a transceiver for a DAC cable?
No. A direct attach copper cable has the transceivers built into its ends, so it plugs straight into the QSFP or SFP cages without separate optics. DAC is the usual choice for short in-rack links, and optical modules for anything longer.
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