Twisted Pair Cabling and 10 Gigabit Cabling


Certifying a twisted pair copper cabling system for the deployment of 10 Gigabit per second Ethernet.
Today, 10 Gigabit/sec Ethernet (10 GbE) finds application over fiber optic cabling in the data center, in riser cabling, and in campus backbones, but widespread use of 10 GbE over twisted-pair copper cabling (10GBASE T) is going to take off soon. Active devices like switches, servers, and NIC cards are becoming available to support 10GBASE-T. The Institute of Electrical and Electronics Engineers (IEEE) standards committee approved the 10GBASE T standard in June 2006. This standard defines the minimum level of performance for the transmission medium, the twisted pair copper cabling. In addition, the cabling industry developed new cabling standards, Augmented Category 6 (Cat 6A) and Augmented Class E (Class EA), to support a new generation of very high throughput network technologies such as 10 GbE.

Certification and Standards
Certification of the cabling system provides the assurance that that the installed cabling system delivers the bandwidth and performance needed for the reliable operation of 10GBASE T before the expensive high performance network devices are purchased and installed.

Existing Cat 6 or Class E cabling system may satisfy the 10GBASE-T requirements established in IEEE std. 802.3. These legacy cabling systems are limited in the length over which they meet the transmission requirements. Re-certification of these installed links against the IEEE 802.3 requirements (also TIA-TSB155 or ISO TR 24750) delivers the definitive answer. The augmented cable types have been developed to support the full 100 m channel for 10-GBASE-T.

Test Parameters
Field certification of installed twisted-pair cabling for 10GBASE T includes all the test parameters that are specified in the TIA/EIA-568-C and ISO 11801 standards for Category 6/Class E links. Table 1 lists these test parameters. The major change for 10 GbE is that the frequency range for these tests now extends to 500 MHz in order to support the higher data rates of the 10 GbE signaling technology. The new cabling standards refer to the legacy test parameters listed in table 1 as the “In-Channel” test parameters. We must add to these legacy test parameters, alien crosstalk test parameters to complete the field-certification effort for 10GBASE-T.

Test Parameter – ‘Old’ NameTest Parameter – ‘New’ Name
Insertion Loss (IL)Insertion Loss (IL)
Near End Crosstalk (NEXT)Near End Crosstalk (NEXT)
Power Sum Near End Crosstalk (PS NEXT)Power Sum Near End Crosstalk (PS NEXT)
Attenuation to Crosstalk Ratio (ACR)Attenuation to Crosstalk Ratio – Near End (ACR-N)
Power Sum Attenuation to Crosstalk Ratio (PS ACR)Power Sum Attenuation to Crosstalk Ratio – Near End (PS ACR-N)
Far End Crosstalk (FEXT)Far End Crosstalk (FEXT)
Equal Level Far End Crosstalk (ELFEXT)Attenuation to Crosstalk Ratio – Far end (ACR-F)
Power Sum Equal Level Far End Crosstalk (PS ELFEXT)Power Sum Attenuation to Crosstalk Ratio – Far End (PS ACR-F)
Return Loss (RL)Return Loss (RL)
Wire MapWire Map
Propagation DelayPropagation Delay
Delay SkewDelay Skew
LengthLength


Alien Crosstalk
Alien crosstalk takes place between wire pairs in different, adjacent cabling links. Therefore, the Alien Crosstalk test parameters are referred to as “Between-Channel” test parameters. Alien crosstalk may occur between any two-wire pairs in a cabling bundle. The combined impact of all wire pairs in the bundle upon the wire-pair-under-test have to be measured. The test parameter to capture this combined impact are power sum alien near end crosstalk (PS ANEXT) and power sum alien attenuation-to-crosstalk-ratio from the far end (PS AACR-F). Alien crosstalk is the most significant disturbance or noise source for the 10GBASE-T application over twisted pair cabling. The alien crosstalk performance will determine the distance limit for installed Cat 6 or Class E cabling.

The Fluke Networks’ DTX-1800 CableAnalyzer™ tester fully supports the field certification process of twisted pair cabling against the IEEE std. 802.3 or the cable industry standards. The DTX-1800 not only performs the “In-Channel” link performance but also the “Between-Channel” alien crosstalk performance. Details about the test methodology and the test parameters are described in the white paper “How to Certify Twisted-Pair Cabling for 10 Gbps Ethernet”.

Conclusion
Proper certification of any cabling system whether new or old, delivers the definitive answer whether the system as installed will support 10GBASE-T. Choose the IEEE standard (criteria) to certify installed Cat 6 or Class E cabling. The new augmented cabling system should of course meet the requirements established in the new standards. These requirements exceed the 10GBASE-T performance requirements.