Copper 10G Ethernet
Copper 10G Ethernet can run over twin-ax cabling, twisted pair cabling, and backplanes. Common forms
of 10GbE copper cables include:
10GBASE-CX4 was the first 10G copper standard, published as 802.3ak-2004. It uses the XAUI 4-lane
PCS (Clause 48) and copper cabling similar to that used by InfiniBand technology. It is specified to work
up to a distance of 15 m (49 ft). Each "lane" carries 3.125 G baud of signalling bandwidth. 10GBASE-CX4
offers the advantages of low power, low cost and low latency, but has a bigger form factor and more bulky
cables than the newer single lane SFP+ standard, and a much shorter reach than fibre or 10GBASE-T.
This cable is fairly rigid and much more expensive than Category 5 or 6 UTP. Shipments of 10GBASE-
CX4 today are very low, although some network vendors offer CX-4 interfaces which can be used for
either 10GBase Ethernet or for stacking of switches at (slightly) higher speeds (e.g., Dell PowerConnect
PCT6200, PCT7000 and the 1G Powerconnect blade switches PCM6220 and PCM6348).
10GBASE-CR: currently the most common type of copper 10GbE cable is the 10GBase-CR cable that
uses an attached SFP+ connector, also known as a Direct Attach Copper (DAC). This fits into the same
form factor connector and housing as the fiber-optic cables with SFP+ connectors. Many 10GbE switches
accept cables with SFP+ connectors, which support both copper and fiber-optic cables. These cables are
available in 1m, 3m, 5m, 7m, 8.5m and longer distances. The most commonly deployed distances are 3m
and 5m.
Passive and Active DAC: Passive copper connections are common with many interfaces. The industry is
finding that as the transfer rates increase, passive copper does not provide the distance needed and
takes up too much physical space. The industry is moving towards an active copper type of interface for
higher speed connections.Active copper connections include components that boost the signal, reduce
the noise and work with smaller gauge cables, improving signal distance, cable flexibility and airflow.
SFP+ Direct Attach is also known as Direct Attach (DA), 10GSFP+Cu, 10GBase-CR, 10GBase-CX1,
SFP+, and 10GbE Cu SFP cabling. Direct Attach uses a passive twin-ax cable assembly and connects
directly into an SFP+ housing. SFP+ DA has a fixed-length cable, typically 3, 5, 7 or 10m in length, and is
low power, low cost and low latency, with the added advantages of using less bulky cables and of having
the (SFP+) small form factor.
Backplane Ethernet (or 802.3ap) is used in backplane applications such as blade servers and
routers/switches with upgradable line cards. 802.3ap implementations are required to operate in an
environment comprising up to 1 meter (39 in.) of copper PCB with two connectors.
10GBASE-KX4 operates over four backplane "lanes" and uses the same physical layer coding as
10GBASE-CX4 (defined in IEEE 802.3 Clause 48).
10GBASE-KR operates over a single backplane "lane" and uses the same physical layer coding as
10GBASE-LR/ER/SR (defined in IEEE 802.3 Clause 49).
10GBASE-T (or IEEE 802.3an-2006) provides 10 Gbit/s connections over UTP or STP cable, at
distances up to 100 metres (330 ft.). Although Category 6a is required to reach the full 100 metres (330
ft.), Category 5e is good for up to 45 metres (148 ft) and Category 6 will reach 55 metres (180 ft).
10GBASE-T cable infrastructure can also be used for 1000BASE-T, allowing a gradual upgrade from
1000BASE-T using auto negotiation to select which speed to use. 10GBASE-T has latency in the range 2
to 4 microseconds, compared with 1 to 12 microseconds on 1000BASE-T. 10GBASE-T uses the IEC
60603-7 8P8C (RJ45) connectors already widely used with Ethernet. Transmission characteristics are
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