Definition of Crosstalk in Network Encyclopedia.

What is Crosstalk?

Crosstalk is a form of interference in which signals in one cable induce electromagnetic interference (EMI) in an adjacent cable. The twisting in twisted-pair cabling reduces the amount of crosstalk that occurs, and crosstalk can be further reduced by shielding cables or physically separating them. Crosstalk is a feature of copper cables only – fiber-optic cables do not experience crosstalk.

Crosstalk (FEXT / NEXT)

The ability of a cable to reject crosstalk in Ethernet networks is usually measured using a scale called near-end crosstalk (NEXT). NEXT is expressed in decibels (dB), and the higher the NEXT rating of a cable, the greater its ability to reject crosstalk. A more complex scale called Power Sum NEXT (PS NEXT) is used to quantify crosstalk in high-speed Asynchronous Transfer Mode (ATM) and Gigabit Ethernet networks.

Far end crosstalk (FEXT)

FEXT measures the interference between two pairs of a cable measured at the far end of the cable with respect to the interfering transmitter.

Minimizing crosstalk

Crosstalk can be a problem for unshielded twisted-pair (UTP) cabling. To minimize crosstalk, make sure that

  • You don’t untwist or sharply bend the UTP cabling
  • The cable ends connected to a patch panel or wall plate are untwisted no more than half an inch


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