How To Select Between SFP, SFP+, SFP28, SFP-DD, QSFP, QSFP+, QSFP28, QSFP56-DD, And OSFP Modules?

Table of Contents

What is SFP, SFP+, SFP28, SFP56, QSFP, QSFP+, QSFP28, QSFP56, and OSFP?

The typical features of these transceiver modules

Reference

Today, 4K, 8K, and even 16K high-resolution TVs are available. Besides, the commercial installation of 5G and AR/VR (augmented reality/virtual reality) will demand significantly larger bandwidth. Meanwhile, there is much improvement in fiber optics. For example, the hot-pluggable, compact transceiver modules, like SFP-, the QSFP-, and the OSFP- families can supply bandwidth varying from 160 Mbps/s to 800Gbps/s. They play essential roles in telecommunication and data communications applications, especially critical in commercial data centers and cloud networks. Questions like SFP, SFP+, SFP28, SFP-DD, QSFP, QSFP+, QSFP28, QSFP-DD, and OSFP could be perplexed. Not to mention the subtle difference between them. Therefore, below we’ll talk about these modules in detail.

Before we start to dive, let’s see the introduction history of these transceiver modules visually from the chart below.

What is SFP, SFP+, SFP28, SFP56, QSFP, QSFP+, QSFP28, QSFP56, and OSFP?

• What is SFP?

SFP, aka small form-factor pluggable, is a compact and hot-pluggable transceiver module. It works as the media between the network equipment and cables, making the photoelectric and electro-to-optical conversion. SFP is commonly used in Ethernet, Fibre Channel, data centers, and cloud networks.

SFP comes with 100Mbit/s, 1 Gbit/s, and 4 Gbit/s versions. The typical is 1 Gbit/s SFP for Ethernet and up to 4 Gbit/s for Fibre Channel.

• What is SFP+?

SFP+ is the first iteration of the SFP module, introduced in 2006, bringing speeds up to 10 Gbit/s. Furthermore, SFP+ makes two SFP+ ports’ direct attach linking possible, enabling DAC (direct attach cable) and AOC (active optical cable) as excellent solutions for the short-distance direct connection between two adjacent network switches.

• What is SFP28?

The SFP28 iteration is the third generation of the SFP series, designed for speeds of 25 gbit/s over a single lane, following the IEEE 802.3by specification (25GBASE-CR). In application terms, there’re six variants, including Dual Fiber SFP28, BiDi SFP28, CWDM SFP28, DWDM SFP28, SFP28 DAC, and SFP28 AOC.

• What is SFP-DD?

The SFP-DD module, also known as “small form-factor pluggable double density,” enables 100Gbit/s over eight transmission lanes. The SFP-DD MSA (multisource agreement association) standard was issued in 2019. Currently 8 × 50 Gbit/s, 8 × 25 Gbit/s, and 8 × 112 Gbit/s SFP-DD112 speeds are available.

• What is 4 Gbit/s QSFP?

QSFP is the acronym for Quad Small Form-factor Pluggable. The QSFP series are compact, hot-pluggable transceiver modules like the SFP series. The 4 Gbit/s QSFP was designed for four channels carrying Gigabit Ethernet, 4G Fiber Channel, or DDR InfiniBand.

• What is 40 Gbit/s QSFP+?

QSFP+ is the subsequent iteration of QSFP, supporting either four 10 Gbit/s channels carrying 10 Gigabit Ethernet, 10G FC FiberChannel, or QDR InfiniBand, or a single 40 Gigabit Ethernet link.

• What is 100 Gbit/s QSFP28?

Also known as “QSFP100” or “100G QSFP” for simplicity, QSFP28 could be used at 100 Gigabit Ethernet, EDR InfiniBand, or 32G Fibre Channel. It is more popular than the competing CFP series. It can either support 4*25G breakout connections or a 1*100G connection.

• What is QSFP56?

Also called “200G QSFP”, QSFP56 follows the exact physical specifications as QSFP28 (SFF-8665) and is compliant with electrical specifications SFF-8024 and revision 2.10a of SFF-8636. It can carry 200 Gigabit Ethernet, HDR InfiniBand, or 64G Fibre Channel.

• What is QSFP56-DD?

As mentioned earlier in SFP-DD, QSFP-DD stands for “Quad Small Form Factor Pluggable Double Density.” Compared to other QSFP series, it adds

an extra row of contacts for an eight-lane electrical interface. QSFP-DD deployed in a single rack unit could provide up to around 14Tb/s bandwidth. It is compatible with QSFP.

• What is an OSFP Transceiver?

OSFP is the acronym for Octal Small Form-factor Pluggable. OSFP MSA first released OSFP in 2016. Then in 2021, its 4.0 version was published. Now it can offer eight high-speed electrical channels at 800 Gbps (8x100G or 2x400G). OSFP 4.0 supports dual 400G and octal 100G breakout modules with dual LC, dual Mini-LC, dual MPO, and octal SN/MDC fiber connector options.

Furthermore, the OSFP MSA is already starting the 200G/Lane Electrical Signaling Group to design 1600G-OSFP, which theatrically could support 200G electrical signaling speed per lane in a backward-compatible fashion.

A technologist at TE Connectivity, Nathan Tracy, said, “1600G-OSFP enables next-generation switch designs with up to 57.6T bandwidth per rack unit.” He added, “It is remarkable that the OSFP can support this level of bandwidth density in a pluggable form factor.”

After introducing these modules, we’d like to specify the shared design features all of them have.

The typical features of these transceiver modules

First, let’s focus on the common characteristics of these transceiver modules. Although there’re lots of articles already dealing with the subject, however, the shared aspects of them are not well touched. Thus, we’d like to highlight this perspective.

• The compact small form factor & higher port density design

It’s straightforward to see why the SFP (Small form-factor pluggable) family replaced the GBIC (Gigabit interface converter). For the simple reason, SFP

is much smaller than GBIC. As Wikipedia mentioned, also known as mini-GBIC, SFP has the same functionality but in a smaller form factor. Introduced in 2001, it essentially made the GBIC obsolete.

The table below lists their respective dimensions and data rates.

id	Dimensions (H x W x D)	Data rate
GBIC	0.39 in. x 1.18 in. x 2.56 in (1 cm x 3 cm x 6.5 cm)	155 Mbps 622 Mbps 1.25 Gbps
SFP family	0.33 in x 0.53 in x 2.22 in (8.5 mm x 13.4 mm x 56.5 mm)	SFP	155 Mbps 622 Mbps 1.25 Gbps 2.5 Gbps 3 Gbps 4.25 Gbps
		SFP+	10 Gbps
		SFP28	25 Gbps
		SFP56	50 Gbps

And the figure below illustrates the comparison in dimensions more vividly.

Out of the same consideration, the QSFP (Quad Small Form-factor Pluggable) family is slightly larger than the SFP family, yet with quatre-fold speeds. Then the competing OSFP is a somewhat larger sibling, allowing for more significant power outputs. For instance, its 2022 released product is capable of 800 Gbit/s links between network equipment.

The table below provides the details information for SFP-, QSFP, and OSFP families.

id	Size (mm2)	Data rates
SFP	113.9	At introduction, typical speeds were 1 Gbit/s for Ethernet SFPs and up to 4 Gbit/s for Fibre Channel SFP modules
SFP+		10 Gbit/s
SFP28		25 Gbit/s
SFP56		50 Gbit/s
QSFP	156	4 Gbit/s
QSFP+		40 Gbit/s
QSFP28		100 Gbit/s
QSFP28-DD		8*25 Gbit/s
QSFP56		4*50 Gbit/s
QSFP56-DD		8*50 Gbit/s
OSFP	slightly bigger	800 Gbit/s

The figure below shows the comparison between QSFP-DD and OSFP.

• The trending lower power consumption

Another popular feature lies in the power consumption of these transceiver modules. Even though the individual gap between the power consumption of two modules is negligible, the total usage of thousands of them is considerable. So, the lower power consumption is desirable.

The table below indicates the maximum power consumption of several transceiver modules.

id	Maximum power consumption
QSFP56	<3.5W
QSFP28-DD QSFP56-DD	<12W
OSFP	<15W

The comparison between these transceiver modules

Since we’ve finished the trending features of transceiver modules, it’s time to talk about the difference between them.

Name	Standard	Introduced	Status	Size (mm2)	Backward compatible	Media	Connector	POWER CONSUMPTION	PRICE	Max channels
100 Mbit/s SFP	SFF INF-8074i	2001-05-01	current	113.9	none	Fiber, Twisted Pair	LC, RJ45	Low	$	1
1 Gbit/s SFP	SFF INF-8074i	2001-05-01	current	113.9	100 Mbit/s SFP*	Fiber, Twisted Pair	LC, RJ45	Low	$	1
10 Gbit/s SFP+	SFF SFF-8431 4.1	2009-07-06	current	113.9	1 Gbit/s SFP	Fiber, Twisted Pair, DAC	LC, RJ45	Slightly bigger than SFP+	$$	1
25 Gbit/s SFP28	SFF SFF-8402	2014-09-13	current	113.9	10 Gbit/s SFP+	Fiber, DAC	LC	Slightly bigger than SFP+	$$	1
50 Gbit/s SFP56			current	113.9		Fiber, DAC	LC	Slightly bigger than SFP28	$$	1
4 Gbit/s QSFP	SFF INF-8438	2006-11-01	current	156	none			Bigger than SFP+	$$	4
40 Gbit/s QSFP+	SFF SFF-8683	2012-04-01	current	156	none	Fiber. DAC	LC, MTP/MPO	Bigger than SFP+	$$$	4
50 Gbit/s QSFP28	SFF SFF-8665	2014-09-13	current	156	QSFP+	Fiber, DAC	LC	Max 6W	$$$	2
100 Gbit/s QSFP28	SFF SFF-8665	2014-09-13	current	156	none	Fiber, DAC	LC, MTP/MPO-12	Max 6W	$$$	4
200 Gbit/s QSFP56	SFF SFF-8665	2015-06-29	current	156	none	Fiber, DAC	LC, MTP/MPO-12	Max 6W	$$$	4
400 Gbit/s QSFP-DD	SFF INF-8628	2016-06-27	current	156	QSFP+, QSFP28	Fiber, DAC	LC, MTP/MPO-16	Max 12W	$$$	8
400Gbit/s 800Gbit/s OSFP	OSFP MSA2016	2016	current	Slightly bigger than QSFP	none	Fiber, DAC	LC, MTP/MPO-12	Max 15W	$$$$	8

References

Wikipedia. “Gigabit Interface Converter,” December 12, 2021. https://en.wikipedia.org/wiki/Gigabit_interface_converter.

‌Wikipedia Contributors. 2022. “Small Form-Factor Pluggable Transceiver.” Wikipedia. Wikimedia Foundation. April 25, 2022. https://en.wikipedia.org/wiki/Small_form-factor_pluggable_transceiver.

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