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10G Twinax SFP+ DAC Cable Buying Guide

AuthorAiyden

Date04/20/2022

DAC cable is a cost-effective equivalent for optical transceivers in high-speed data communication. This post is SFP+ DAC wiki and guides how to buy the best 10G Twinax SFP+ DAC cable.

High-speed cable has vast adoption in the switch-to-switch, switch-to-server, and server-to-storage market. According to the data by GlobeNewswire, the switch-to-switch segment in 2020 has a market share of 64.3%, and DAC cable in 2020 has a market share of 32.4%. Besides, the high-speed cable market will see a 6.9% CARG from 2021 to 2028. With the benefits of low cost and low power consumption, Twinx direct attach copper cable is becoming more and more popular in high-speed Ethernet interconnections. This post will guide you to buy SFP+ DAC cable for your business needs.

 


What is the 10G Twinax SFP+ DAC Cable?

An SFP+ direct attach copper (DAC) cable is a Twinax copper cable with fixed SFP+ connectors terminated on both ends. The built-in SFP+ connector module on the direct attach copper cable is identical to the standard SFP+ transceiver. However, there is no optical Laser in DAC connectors and no need for a matching extra fiber patch cable. Hence DAC cable is a cost-effective equivalent for costly optical transceivers in high-speed data communication.

 

 

Fig 1: Solution 1 of using 10G SFP+ DAC cable vs Solution 2 of using a pair of 10GBASE-SR SFP+ modules and an OM3 fiber for server-to-switch interconnection.

 

Note: IEEE doesn't standardize high-speed cables. 10GSFP+Cu or 10GBASE-CR is another name for Twinax SFP+ cable.

 

Server-to-switch Products Price
Solution 1
① 7m 10G SFP+ DAC US$ 12.90
Total Cost US$ 12.90
Solution 2
② A pair of 10G SR SFP+ modules US$ 6.90 × 2
③ 7m OM3 multimode fiber US$ 5.60
Total Cost US$ 19.40

 


What is the 10G Twinax SFP+  DAC Cable Used for?

Growing devices and data requests from the Internet puts pressure on high-bandwidth and high-density applications, which drive server virtualization technology to achieve multiple virtual devices connected to one host server. Accordingly, more massive data are transmitted from the server to switch to meet the requirement of the end devices. This is where the direct attach copper cable comes in. 

 

 

Fig 2: 10G SFP+ to 10G SFP+ DAC cable and 40G QSFP+ to 4× 10G SFP+ breakout DAC cable application.

 

The DAC cable with copper cable as medium decides its short length. Generally speaking, a 10G SFP+ cable link is within 10m while a 10G SFP+ AOC cable can reach 100m. It is noted that the transmission distance high threshold of the DAC cable is affected by the cable data rate. The higher the speed, the shorter the max transmission distance. The distance restriction of SFP+ Twinax cable makes it ideal for short-range interconnection between two devices placed in the same rack for 10 Gigabit Ethernet applications, typically data center server-to-switch or storage-to-switch connection in top of rack (ToR) architecture.

 

 

Fig 3: Twinax DAC cables for ToR interconnect applications

 

In such a short interconnection, using 10G DAC is more cost-effective than deploying AOC cables for the following reasons:

 

Better Heat Dissipation: copper cable has better heat dissipation.

Energy Saving: active DAC has a low power consumption value of around 440mW and almost zero power consumption for passive DAC since it requires no power supply; the power consumption of active optical cable (AOC) is about 2W.

Lower Price: DAC is cheaper than AOC, as the cost of fiber is higher than copper cable.

 


What Factors to Consider When Buying Twinax SFP+ Cable?

 Active vs passive, direct vs breakout are two classifications of 10G SFP+ direct attach copper cable. Besides, one should concern about other factors such as wire AWG, vendors, and budget to buy the best SFP+ copper cable.

Twinax Active vs Passive

Twinax active or passive cables describe whether an electronic circuit is built-in to boost signal quality. Active Twinax DAC cable has equipped electronic components in the SFP+ connector while passive Twinax DAC cable has none.

 

Taking transmission distance, power consumption, and signal performance into account when choosing between passive vs active DAC SFP+ cable. 

 

Transmission Distance

In general, the max transmission distance of passive SFP+ DAC cable is 7m. However, the active SFP+ DAC cable can reach up to 10m. Hence for application scenarios requiring more than 7m links, the active Twinax cable may be the better choice.

 

Power Consumption

DAC cable has a low power consumption feature, there is a further distinction between active and passive DAC. The estimated power consumption of the active 10G SFP+ cable is about 440mW. There is nearly zero power consumption of the passive Twinax copper cable. Taking the power-saving advantage to the utmost, give priority to the passive 10G DAC cable.

 

Signal Conditioning

Since passive SFP+ DAC cable contains no electronic circuits for signal amplification in its connectors, it relies on the external host equipment (switch) to provide signal conditioning. So to let passive DAC work, the connected switch should have the integrated signal conditioning feature and support the passive DAC cable. When plugging the passive SFP+ cable into a passive cable compatible switch port, the switch will read the module and detect the passive DAC, then activate the signal conditioning function. 

 

Most switches on the market have integrated the signal conditioning into their switch SFP+ ports, so passive SFP+ cable is popular. However, there are a few switches that don't support passive Twinax cable. In this case, the active DAC cable should be matched used to supply itself with the signal conditioning feature.

 

Making a decision between Twinax active or passive cable, one should make a comprehensive assessment of the above factors. In brief, compared to passive Twinax DAC cable, active Twinax DAC cable costs more and saves less power, but can reach longer and provide itself with signal conditioning capacity. 

Connector Type - SFP+ to SFP+ vs QSFP+ to 4 SFP+

SFP+ DAC comes in two types based on the terminated connectors. One is the direct DAC cable with symmetrical SFP+ to SFP+ connectors, the other is breakout QSFP+ to 4× SFP+ connectors. 

 

SFP+ to SFP+ DAC Twinax cable is best for the switch to server direction connection in 10 Gigabit Ethernet applications.

 

40G QSFP+ to 4× 10G SFP+ DAC Twinax cable supports a 40GbE connection at the top rack and distributes 40GbE into four separate 10GbE links to the server, switch, or routers. The most typical application scenarios are short-range carrier or data center interconnection within server room for up to 40Gbps.

 

 

Fig 4: QSFPTEK 10G SFP+ to 10G SFP+ DAC cable vs 40G QSFP+ to 4× 10G SFP+ breakout DAC cable.

Wire AWG - 30/28/26/24 AWG

American wire gauge (AWG) is a matrix to measure the copper wire diameter. The bigger the AWG value, the thinner the wire, and the more the signal loss. DAC cables in the market are available for 30AWG, 28AWG ( 7/0.12mm), and 24AWG (7/0.20mm). Bigger AWG has a smaller bend radius. Wire AWG also influences the cable length, one rule of thumb — the longer the reach, the smaller the AWG. So remember to check the cable installation environment and link distance, pick an AWG value to meet the bending requirement, and be cautious not to exceed the minimum bend radius in a real application.

 

Wire AWG Min. Bend Radius
24 1.5 inches (38 mm)
26 1.3 inches (33 mm)
28 1.0 inches (25 mm)
30 0.9 inches (23 mm)

OEM vs Third-Party Compatible

The key point is compatible DAC cables from third-party vendors are an affordable equivalent for OEM Twinax SFP+ cables. Since the brand system vendor provided cables are expensive. For example, the Cisco DAC cable SFP-H10GB-CU7M price on ITprice is US$ 310.00. Please refer to Why Choose Third-Party Transceiver Modules? for more details.

 

Type
 
Model
OEM Compatible
ITprice sale price QSFPTEK sale price
passive SFP-H10GB-CU7M $310.00 US$ 12.90
active SFP-H10GB-ACU7M $188.00 US$ 26.58

Budget & Price

When purchasing SFP+ DAC cables, you need to keep your budget in mind. Through the above narration, you already know how different SFP+ Twinax cable types affect their price. For instance, QSFPTEK provided active Twinax DAC cable costs more than 1.5 times the passive one at the same length.

 

Note: QSFPTEK website doesn't list active DAC cables, please talk to our sales expert to get a quote.

 

in addition to considering the price of individual products, you also need to consider the overall investment of the system solution — matching products and the future upgrade resilience.

 


Final Words

10G SFP+ cables own the advantages of low-cost, low power consumption, and low latency, the restriction is transmission distance. Hence SFP+ Twinax cables are for direct 10GbE connection between active equipment such as switches, routers, servers, and storage that are located closely in the same data rack. To choose the best SFP+ DAC cable for your business, take factors such as distance, power consumption, and signal conditioning into consideration for choosing passive or active Twinax cable, besides, double-check wire AWG, connector types, vendors and price before making a decision. 

 

QSFPTEK offers DAC cables with a wide selection, ranging from 10G to 100G, 1m to 10m, passive to active, and direct to breakout. All are guaranteed by the QT quality assurance program and provide users with the industry-leading price. Check the price list for reference.

 


QSFPTEK DAC Cable Options

DAC Cable Image Connector Type Price (1M)
10G SFP+ DAC 10G SFP+ to 10G SFP+
$5.10
25G SFP28 DAC 25G SFP28 to 25G SFP28 $14.80
40G QSFP+ DAC 40G QSFP+ to 40G QSFP+ $14.00
100G QSFP28 DAC 100G QSFP28 to 100G QSFP28 $24.70
Breakout 40G QSFP+ 4SFP DAC 40G QSFP+ to 4x 10G SFP+ $17.30

 

 

 

 

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