transceiver modules
How-To

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

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.

history of the introduction of transceiver modules
history of the introduction of transceiver modules

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.

transceiver modules
transceiver modules

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.

GBIC vs. SFP
GBIC vs. SFP

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 size comparison between QSFP-DD and OSFP
the size 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.

idMaximum 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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