Active cables are

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

cables for data transmission that use an

electronic circuit An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electrical ...

to boost the performance of the cable. Without an electronic circuit, a cable is considered a passive cable. Passive cables are liable to degrade the data they carry, due to channel impairments, including

attenuation In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable att ...

crosstalk In electronics, crosstalk is any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, induc ...

and

group velocity The group velocity of a wave is the velocity with which the overall envelope shape of the wave's amplitudes—known as the ''modulation'' or ''envelope'' of the wave—propagates through space. For example, if a stone is thrown into the middl ...

distortion. In active cables, a circuit using one or several

integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...

s 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 transmit data faster than their passive equivalents. Active cables are used in enterprise networks which form the backbone of modern data communication systems, and also to interconnect

consumer A consumer is a person or a group who intends to order, or uses purchased goods, products, or services primarily for personal, social, family, household and similar needs, who is not directly related to entrepreneurial or business activities. T ...

devices such as

camera A camera is an Optics, optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), ...

gaming console A video game console is an electronic device that outputs a video signal or image to display a video game that can be played with a game controller. These may be home consoles, which are generally placed in a permanent location connected to a t ...

s, and

HDTV High-definition television (HD or HDTV) describes a television system which provides a substantially higher image resolution than the previous generation of technologies. The term has been used since 1936; in more recent times, it refers to the g ...

s. Embedding circuitry in cables can allow for less copper to be used in cable production for the same performance, reducing the weight of the cable by as much as 80%, and reduce cable size. Other benefits include longer reach and lower power consumption.

Consumer electronics

Active cables are more compact and portable than passive cables, and as such, they are ideal for use with products such as smartphones, HDTVs, gaming consoles, and DV cameras.

DisplayPort DisplayPort (DP) is a digital display interface developed by a consortium of PC and chip manufacturers and standardized by the Video Electronics Standards Association (VESA). It is primarily used to connect a video source to a display device su ...

is the latest consumer electronics standard that has enabled support for active cables by allocating power supply pins inside the connector. Active DisplayPort cables enable ultra-thin (32 AWG and thinner) and long-reach interconnects which are particularly valuable for the use with the miniature

Mini DisplayPort The Mini DisplayPort (MiniDP or mDP) is a miniaturized and less common version of the DisplayPort audio-visual digital interface. It was announced by Apple in October 2008, and by early 2013 all new Apple Macintosh computers had Mini DisplayPo ...

form-factor.

Enterprise and storage applications

Active cables play an important role in enterprise and storage applications due to the confined space and air-flow requirements in

data centers A data center (American English) or data centre (British English)See spelling differences. is a building, a dedicated space within a building, or a group of buildings used to house computer systems and associated components, such as telecommunic ...

and long reaches (up to 30 meters) required to make some of the rack-to-rack connections. Because active cables can facilitate thin cable gauges, a tighter bend radius results, which can give cables in these applications easier maneuverability and improved airflow. Active cable adoption in data centers has been growing steadily. For example, as of 2010, half of

SFP+ Small Form-factor Pluggable connected to a pair of fiber-optic cables Small Form-factor Pluggable (SFP) is a compact, hot-pluggable network interface module format used for both telecommunication and data communications applications. An SF ...

interconnect volume is in active cables (as opposed to passive copper cables and optical transceiver modules). The advent of QSFP (Quad SFP) interconnects for 40 Gigabit Ethernet and

InfiniBand InfiniBand (IB) is a computer networking communications standard used in high-performance computing that features very high throughput and very low latency. It is used for data interconnect both among and within computers. InfiniBand is also used ...

is driving the widespread adoption of active cables in this form-factor as well.

Standards

InfiniBand

Serial Attached SCSI
(SAS)
DisplayPort

PCI Express

HDMI

USB

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 In wireless communications, channel state information (CSI) is the known channel properties of a communication link. This information describes how a signal propagates from the transmitter to the receiver and represents the combined effect of, for ...

link adaptation Link adaptation, comprising adaptive coding and modulation (ACM) and others (such as Power Control), is a term used in wireless communications to denote the matching of the modulation, coding and other signal and protocol parameters to the conditio ...

. Another criticism of active cables is that manufacturers may patent the electronics inside an active cable or even utilize on-chip

cryptography Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adver ...

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 their passive counterparts. 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.

References

{{Reflist Signal cables

Consumer electronics

Enterprise and storage applications

Standards

Criticism

See also

References