| Eliminating alien crosstalk - June 09 |
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June 22, 2009Testing should be performed in the field when deploying 10GBase-T By Dan Payerle Alien crosstalk describes the general phenomenon where energy is coupled between cables in a common bundle or installation. It was brought to light by the development of active network hardware that could provide 10G Ethernet over twisted-pair cabling (10GBase-T). Alien crosstalk becomes worse as the operational frequency increases. Since the frequency range required to support 10GBase-T is higher than that of 1000Base-T, crosstalk—both internal and alien—has become a difficult obstacle to overcome when designing and installing LAN cabling to support the latest technologies. Mitigation techniques 1. Proximity is the key contributor to alien crosstalk. When 10GBase-T is being selectively deployed, avoid using adjacent ports in the patch panel. There may be no alternative, however, when deploying 10GBase-T to workstations located near each other. 2. When deploying 10GBase-T in adjacent ports of a patch panel, alien crosstalk testing should be performed in the field. 3. In the event the alien crosstalk test fails, take the following actions to reduce the level of alien crosstalk.
a) Separate equipment and patch cords and unbundled horizontal cables to increase the space between the cables.
b) If the cords cannot be separated, use either Cat 6A or Cat 6 screened twisted-pair (ScTP) cords. c) Reconfigure any cross-connect as an interconnect. d) Replace Cat 6 connecting hardware with Cat 6A. e) Replace the Cat 6 horizontal cable with Cat 6A. 4. Retest the channel after performing any mitigation techniques to be sure that the techniques have brought the alien crosstalk margins back to acceptable levels. |
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