From SFP to QSFP28: What's the Difference Between 5 Optical Module Form Factors?

SFP, SFP+, SFP28, QSFP+, and QSFP28 — these are all optical module form factors. These hot-pluggable transceivers are used to connect network switches and other network devices (such as servers) for data transmission. Before we get into the differences, let's first understand what each of these form factors actually is. YXFiber will walk you through them one by one.

1. SFP

SFP stands for Small Form Pluggable. You can think of it as an upgraded version of GBIC — it's only about half the size. That smaller size means network devices can pack in more ports. SFP modules support data rates like 155M, 1.25G, and 2.5G, and mostly use LC connectors. They're commonly found in SONET/SDH networks, Fast Ethernet/Gigabit Ethernet, and other low-speed transmission applications.

2. SFP+

SFP+ looks exactly the same as SFP — same size, same shape — but it's faster. It supports data rates like 6G, 8G, and 10G. Products that use this form factor include 6G/8G FC optical modules, 10G optical modules, 10G copper RJ45 modules, 10G DAC cables, and 10G AOC cables. SFP+ is widely used in data center 10G Ethernet links (10GBASE-SR).

3. SFP28

SFP28 is basically SFP+ on steroids. Same size, but faster — it pushes up to 25Gbps per channel. SFP28 was built to make network upgrades easier. Going from 10G to 25G and then to 100G? SFP28 gets you there without the hassle.

4. QSFP+

QSFP+ runs 4 channels at the same time, each at 10Gbps, adding up to 40Gbps total. Compared to SFP+, QSFP+ gives you four times the speed. If you're building a 40G network, QSFP+ is the way to go — it saves you money and keeps port density high.

5. QSFP28

QSFP28 was made for 100G applications. It also runs 4 channels at once, but each channel runs at 25Gbps, adding up to 100Gbps total. It supports 100G Ethernet (4×25Gbps) and EDR InfiniBand applications.

Now that we've covered each one, YXFiber will walk you through the key differences. In terms of data rate: SFP is generally for modules under 3G; SFP+ is for modules running 6G to 16G; SFP28 is for 25G/32G modules; QSFP+ is for 40G/56G modules; and QSFP28 is for 100G modules.

In terms of built-in components: SFP, SFP+, and SFP28 use a single laser and a single detector, while QSFP+ and QSFP28 use 4-channel laser and detector arrays. Also, the interface protocols differ across all five form factors.

That wraps up YXFiber's overview of the 5 form factors. Size-wise, SFP, SFP+, and SFP28 are smaller than QSFP+ and QSFP28 (which are the same size as each other). Comparing the data rates and sizes across these form factors, one thing becomes pretty clear: the whole trend in optical modules is about squeezing more bandwidth into smaller packages.