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We are already starting to see the introduction of 10 Gigabit Ethernet copper transmission. Whilst specifiers of structured cabling systems are familiar with the need to plan cabling which can support the necessary bandwidth, few are aware of implications that the cabling choice can have on power consumption over the lifetime of the installation.
Power back-off capability is built in to 10G-BaseT chipsets. Because copper cabling naturally attenuates the transmission signal, shorter cable runs require less power to ensure the signal reaches the other end. Initially designed to mitigate the effects of Alien Crosstalk, the Power Back-Off feature determines the “length” of the cable by measuring the insertion loss and reduces (backs off) the power so that only the required level is supplied.
Based on tables relating to the insertion loss measured, power back off for a typical 30 metre Category 5e (Class D) link would be 12db. However, for a Nexans LANmark-7A (Class FA) link, power could be reduced by a further 2dB.
This has the potential to reduce the transmission power required by 1 or 2 watts per port. When this is multiplied by the high volume of switch ports found in a Data Centre this equates to a significant power and cost saving every minute, every day, every week, every month and every year long after the cabling has been installed!
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