What are the differences between SFP, SFP+, QSFP and QSFP+?

There’s a lot to consider when building a fiber optic network. There are so many different ways to approach optical communication, and every device has its own list of pros and cons. In modern, dense networks, small form factors are a constant necessity. Without such interfaces, you simply can’t pack enough networking components into the limited space that is always constricting the network’s design. That’s why so many form factors have emerged. This simple guide is going to help you map the differences between SFP, SFP+, QSFP and QSFP+. With it, at least some of your networking decisions should come a little more easily.

How Do Compact Fiber Transceivers Compare?

There are four form factors that are substantially more popular than the rest in the world of fiber connectivity. The original is SFP, and variations and improvements to the concept have been integrated over the years. The four incarnations that still see the most use are compared below.

SFP

The acronym stands for “small form-factor pluggable.” As such, SFP connections are small and hot-pluggable. The connectors were originally designed to take up less space in crowded networks to allow for higher traffic density. They run on an LC interface and are half the size of the preceding GBIC form factor. SFP transceiver modules support SONET, Gigabit Ethernet, Fibre Channel and other common interfaces. They can manage traffic from 1 to 10 Gbps across copper and fiber cables. This makes SFP one of the most versatile connectors on the market.

SFP+

SFP+ takes the benefits of the SFP design and improves on their data capacity. SFP+ still functions with copper and optical cabling, but it can achieve much higher speeds. Data rates start at 10 Gbps, and on the newer Fibre Channel design, SFP connections can hit speeds up to 32 Gbps.

QSFP

Another expansion on the original SFP concept, QSFP uses double fiber pairs. The Q stands for “quad,” and the additional pair allows for substantially more powerful data transmission. QSFP connectors are still small and hot-pluggable, and they still support Ethernet and fiber optics. Added to the supported list is InfiniBand.


QSFP data rates get up to 1 Gbps per channel, allowing for 4X1 G cables and stackable networking designs that achieve better throughput.

QSFP+

QSFP+ is the modern incarnation of QSFP. In most data centers, it has completely replaced its predecessor. QSFP+ can reach speeds of 10 Gbps per line. This makes it a 40G connection type that still maintains the small form factor that is essential to so many network designs.


The latest advance on QSFP connections is QSFP28. It expands on the transmission rate per line, and it easily gets throughput beyond 100G.

How Do You Choose Between SFP, SFP+, QSFP and QSFP+?

Selecting the right connector is essential to building a network that functions correctly at an efficient price point. While it won’t always be easy to make the decision, there are a few considerations that can completely dictate what you use.

How Much Traffic Does Your Network Handle?

As you just read, the capacity of each form factor is pretty different. If you’re running a high-end data center, you’ll probably need QSFP+ and possibly even QSFP28. For lower demands, the other forms might suffice.


It’s also important to anticipate traffic growth. It might feel good to save money and go with lower capacity now, but if you’re going to have to make major replacements in two years, then there is no real saving taking place. Weighing the value of future-proof networking equipment is always one of the hardest parts of design.

How Long Is Your Network?

SFP and all of its variants work with both single and multi-mode fiber. So, the physical length of your network might determine which of the modes you’ll be utilizing. Then again, if all of the form factors support both modes, why does it matter?


It comes down to cost. If you have to invest in the higher cost of single-mode fiber, it might be prudent to downscale the connector. Conversely, a shorter, multi-mode network might leave room in the budget for future proofing and bigger data capacity.

How Hot Is Your Network?

It’s pretty simple math. Adding channels and data throughput increases the heat of the system. It’s inevitable. Planning around cooling costs and heat management can help you determine when and where to invest in higher data rates or make cuts.


The variable forms of SFP are easy enough to separate. Each has its own set of benefits and drawbacks, and all of them are still widely in use today.