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What is the maximum length of SFP+ cable?
Knowledge Base + 2023.12.07

SFP+ DAC twinax cable is a copper interconnect using a twinax cable assembly that connects directly into the SFP+ housing. By directly connecting two SFP+ slots, it effectively eliminates the cost-prohibitive optical transceiver required in the equipment, and greatly reduces the power consumption, latency and installation time. 10G SFP+ DAC twinax cable with a max length of 10 m is commonly used in intra-rack and inter-rack connections: including interconnection of top-of-rack switches with servers and storage devices within a rack or in adjacent racks.


Figure 1: FS SFP+ DAC cables

Can I Use SFP+ DAC Twinax Cable in SFP Ports?

Yes, SFP+ cables are backward compatible to SFP ports and will work fine.

Can I Use a Compatible SFP+ DAC Twinax Cable on Cisco Switches?

Yes, just like optical transceivers, you should not worry about DAC cable compatibility. All the compatible SFP+ DAC twinax cables are made with the same industry standard as the Cisco cables. A qualified SFP+ DAC copper cable should be tested and be fully recognized by Cisco equipment to ensure proper function. Get a reliable direct attach cable manufacturer to buy SFP+ DAC twinax cable, so your compatible SFP+ DAC cable can perform equally great as the branded one—with significantly reduced cost.

Passive or Active SFP+ DAC Twinax Cable?

Passive SFP+ DAC twinax cable contains no electrical components, thus requires little or no power to operate. SFP+ active copper cable, on the contrary, needs DC power to integrates signal processing circuitry into its built-in connectors, making it more expensive. It is recommended to use passive SFP+ DAC when the distance is no more than 7m. As for link distance greater than 7 m (like ToR to EoR), active DACs would be required.

DAC Cable Max Length?

SFP+ DAC can only provide a maximum distance of 10 meters (about 33 feet) based on active copper cables. If the distance is not a problem, the SFP+ DACs tends to be an optimal option because of lower power consumption and lower latency. Read Guide to 10G DAC & AOC Cables for more information about AOC and DAC cables max length.

 What is SFP Connector?

SFP connector or SFP plug is another name of SFP as SFP (small form-factor pluggable) is a compact and hot-pluggable interface connector. The SFP connector module functions as the intercommunication media between the network devices and cables to achieve photoelectric and electro-to-optical conversion. SFP interface is commonly used in SFP port network equipment such as Ethernet switches, firewalls, routers, network interface cards (NICs) for both data communication and telecommunication applications.


Figure: the optical interface of the 1000BASE-SX SFP connector module is located at the side of the dust cap. Once unplug the cap, will you see the optical interface.

According to transmission media, there are SFP copper connectors and SFP fiber connectors. Copper SFP uses an RJ45 SFP connector interface, whereas fiber SFP uses SFP lc connector, SFP sc connector, and SFP MTP/MPO connector interface as typical ones. According to the SFP forms, different SFP form factors often utilize corresponding SFP connectors.

The table below shows the SFP connector interface types for different SFP types.

SFP TypesMediaConnector
100 Mbit/s SFP
LC, RJ45
1 Gbit/s SFP
Fiber, copper
1 Gbit/s cSFP
10 Gbit/s SFP+
Fiber, copper, DAC
LC, RJ45
25 Gbit/s SFP28
Fiber, DAC
50 Gbit/s SFP56
Fiber, DAC
4 Gbit/s QSFP

40 Gbit/s QSFP+
Fiber, DAC
50 Gbit/s QSFP28
Fiber, DAC
100 Gbit/s QSFP28
Fiber, DAC
200 Gbit/s QSFP56
Fiber, DAC
400 Gbit/s QSFP-DD
Fiber, DAC

What Type of Connector is Used with an SFP Port?

SFP ports are frequently found in Ethernet network switches. These switches with 1G SFP ports as the major functional switch ports are called gigabit SFP switches.

SFP port on SFP switch supports both SFP copper connector and SFP fiber connector while RJ45 port can only take copper SFP module RJ45 connector. SFP connector types that 1G SFP port can take are RJ45 SFP connector, SFP lc connector, SFP sc connector.

FAQs about SFP Transceiver

Can We Use SFP Hardware in SFP+ Slots?

In many cases, the SFP+ port accepts SFP optics, but the speed will be down to 1G instead of 10G. However, SFP+ optics can not be plugged into the SFP port, because SFP+ does not support speed under 1G. In addition, almost all SFP+ ports on Cisco switches can support SFPs, but many SFP+ ports of Brocade switch only support SFP+ optics.

Can I use a 1000base-LX sfp for 1000base-SX fiber?

Generally, they are not interchangeable. 1000Base SX and LX are two optics standards with different operation wavelengths.1000Base LX SFP transceiver usually operates at 1310nm and uses single-mode fiber to connect, while 1000Base-SX usually is 850nm SFP and works with multimode fiber.

Can you aggregate multiple SFP ports?

Of course, you can. Link aggregation provides benefits like increased bandwidth, redundancy, and load-balancing. That will ensure that one link can immediately switch to a second available link when it fails. Therefore, aggregation on SFP ports is critical for enterprise networks where performance and security are more important. But note that, before connecting the SFP ports, please make sure that the switches have been configured for link aggregation. Otherwise, it will cause network loops.