What’s twinax?

What’s twinax?
Twinaxial cabling, or "Twinax", is a type of cable similar to coaxial cable, but with two inner conductors instead of one. Due to cost efficiency it is becoming common in modern very-short-range high-speed differential signaling applications.

Applications?

SFP+ Direct Attach (10GSFP+Cu)
This is a copper 10 Gigabit Ethernet cable that comes in either an active or passive twin-ax cable assembly and connects directly into an SFP+ housing. The active twin-ax cable has active electronic components in the SFP+ housing to improve the signal quality; the passive twin-ax cable is just a straight “wire” and contains no active components. Generally twin-ax cables that are less than 5 meters in length are passive and greater than 5 meters in length are active but this is a general rule of thumb and will vary from vendor to vendor. SFP+ Direct Attach is expected to be the optimum solution for reaches of 10 m.

One of major applications includes Arista Networks and Cisco Systems implementation coupled with SFP+ modules. This type of connection is able to transmit at 10 Gigabit full duplex speed over 5 meter distances. Moreover this setup offers 15 to 25 times lower transceiver latency than current 10GBASE-T CAT6/CAT6a/CAT7 cabling systems: 0.1 ?s for Twinax with SFP+ versus 1.5 to 2.5 ?s for current 10GBASE-T specification. The power draw of Twinax with SFP+ is around 0.1 watts, which is also much better than 4–8 watts for 10GBASE-T.
As always with cabling one of the consideration points is Bit error ratio or BER for short. Twinax copper cabling has BER better than 10?18 according to Cisco, and therefore is acceptable for applications in critical environments.
This SFP+/Twinax is also referred to as 10GBASE-CR by some manufacturers, even though there is no IEEE or other standard with that name.

SATA-3 Cables
Some SATA-3 cables are implemented using twin-ax.

DisplayPort
Many manufacturers of DisplayPort cabling are also using twinaxial configurations to accommodate the strict insertion loss, return loss, and crosstalk requirements for the 2.7 Gbit/s signaling rate.