Active cable

Active cables are copper cables used for data transmission that use an electronic circuit to boost their performance. Without an electronic circuit, a cable is considered passive. Passive cables are prone to data degradation from channel impairments, including attenuation, crosstalk, and group velocity distortion. In active cables, a circuit using one or several integrated circuits is embedded in the cable to compensate for some or all of these impairments. This active boosting allows cables to be more compact, thinner, longer, and to transmit data faster than passive cables.

Active cables are used in enterprise networks, which are extremely common in modern data communication systems. They are also used to connect consumer devices such as cameras, gaming consoles, and HDTVs.

Embedding circuitry in cables can allow for less copper to be used in cable production while still retaining performance. This reduces the weight of the cable by up to 80%. Other benefits include longer reach and lower power consumption.

Consumer electronics
Active cables are more compact and portable than passive cables, making them ideal for use with products such as smartphones, HDTVs, gaming consoles, and DV cameras. DisplayPort is the latest consumer electronics standard to support active cables by allocating power supply pins inside the connector. This advancement enable ultra-thin (32 AWG and thinner) and long-reach interconnects which are particularly valuable for the use with the miniature Mini DisplayPort form-factor.

Enterprise and storage applications
Active cables are important in enterprise and storage applications due to the confined space and air-flow requirements in data centers and the long distances(typically up to 30 meters) between some of the rack-to-rack connections. Because active cables can facilitate thin cable gauges the cables have a tighter bend radius, which can give cables in these applications easier maneuverability and allow for better airflow.

Active cable adoption in data centers has been growing steadily. As of 2010, half of SFP+ interconnect volume is in active cables (as opposed to passive copper cables and optical transceiver modules). In addition to this, the advent of QSFP (Quad SFP) interconnects for 40 Gigabit Ethernet and InfiniBand is driving the widespread adoption of active cables in this form-factor.

Standards

 * InfiniBand
 * Serial Attached SCSI (SAS)
 * DisplayPort
 * PCI Express
 * HDMI
 * USB
 * Thunderbolt

Criticism
Opponents of active cable technology often criticize the fact that the electronics in an active cable design could be placed inside the connected devices instead, and an inexpensive passive cable used to connect the devices. Digital alternatives to using analog equalizers and impedance matching circuits to improve cable performance also exist, such as channel estimation or link adaptation.

Another criticism of active cables is that manufacturers may patent the electronics inside an active cable or even utilize on-chip cryptography to prevent competitors or consumers from producing their own replacement cables, and therefore enable manufacturers to monopolize the market for cables and charge consumers exorbitant prices. Active cables typically cost 5 to 10 times more than passive cables. Some active cables are only produced by a single manufacturer, and sold through a single distributor. Low cable cost and high availability is desirable because cables are often inadvertently lost or damaged.

Some opponents of active cables also believe that active cables do not provide power savings for signal processing reasons; because in an active cable design, there is at least one extra integrated circuit (IC) compared to passive cable designs. This extra IC must be powered separately, when in a passive cable design, the signal processing can be integrated onto a single chip.