Guidance to Choose Shielded or Unshielded Cabling for 10GBASE-T Network

Twisted pair cables are widely used in transmitting information. The twist in the wire cancels out any magnetic interference that may develop in the wiring. There are two kinds of twisted pair cabling, shielded twisted pair (STP) and unshielded twisted pair (UTP). For 10GBASE-T data transmission with distance up to 100 meters, both STP and UTP copper cabling systems are applicable as it defines in IEEE 802.3an-2006 standard. So which one will you choose for achieving the best performance of your 10GBASE-T network?

UTP doesn’t use any additional shielding, except of the plastic sheath around cable. While STP is a twisted pair cable that is additionally insulated by foil or/and braided copper shielding. For STP and UTP, each has its advantages and disadvantages. The following will talk about their performances in 10GBASE-T network from the sides of alien crosstalk, termination&installation and costs.

Fs cat-6a-utp-and-stp.jpg

 

Alien Crosstalk

In 10GBASE-T applications, it’s alien crosstalk (the noise source) most limits the data transmission performance over copper cable. Because the 10GBASE-T transceiver can’t detect and compensate for noise from adjacent channels. That must be suppressed within the cabling system to ensure reliable data transmission. This noise is measured as power sum alien near-end crosstalk (PSANEXT) and as power sum alien attenuation to crosstalk ratio at the far-end (PSAACRF). Crosstalk should be measured in a 6-around-1 (namely six cables tightly bundled around a center cable) cabling configuration considering the worst-case effect.

In IEEE 802.3an-2006 standard, Cat 6a UTP, Cat 6 STP, and Cat 6 UTP cabling are talked about to support 10GBASE cabling system. For example, Cat 6a UTP cabling, to reduce alien crosstalk, manufactures think about increasing separation between cables and tighter twisted rates or crosstalk suppression within the printed circuit boards as to the connectors. These methods comply with TIA/EIA (Telecommunication Industry Association) standard PSANEXT and PSAACRF specifications for reaching 100m distance. Without these improvements, category 6 UTP system can’t meet the alien crosstalk limits required for 100 meters of 10GBASE-T transmission. For properly installed and bonded STP cabling, foil screens within the cable prevent signals from coupling. Thus, it reduces alien crosstalk below required performance levels. STP cabling system can provide superior alien crosstalk performance.

Fs 100-meter-channel-psanext-performance-characteristics.jpg

 

Termination

STP cable include a shield around each individual pair. Another screened STP cable includes an overall shield or braid , around all pairs with an additional foil around each individual shield. The cable design is able to deliver excellent alien near-end crosstalk performance as there is no crosstalk between pairs since the pairs are individually shielded. But at the same time, STP cable is not easy for termination, resulting in more difficult cable management. Because the foil and drain wire in an STP cable must be pulled back and twisted around the cable end prior to termination. And the unused foils should be trimmed. But for UTP cable, it’s designed as unshielded. So the termination takes longer for STP cabling than UTP.

Bonding and Grounding

Proper structured grounding processes is useful for protecting personnel and expensive equipment. In data centers, most 10GBASE-T compliant copper cabling is installed. So integrity of the bonding and grounding system must be sound to realize the full performance of the system.

The UTP cabling connectivity doesn’t need complete system bonding. But you should consider the integrity of the grounding of the patch panels and racks to the common grounding point to protect the infrastructure. While for STP cabling system, bonding cable to the connectivity components is required to ensure proper performance. For 10GBASE-T data transmission, you should be careful with the implementation of the power and grounding system that the copper data cable system resides in. If the power or cabling system is not properly designed and/or installed, data rate errors are likely to happen. As 10GBASE-T applications are very sensitive to noise, potential differences in electrical grounds can cause bad influence on 10 GbE data transmission. If there are data rate errors within an STP cabling data network, you should better check the bonding and grounding as well as the overall design of the power and ground system.

Costs

The overall cost of STP cabling system is higher than UTP cabling system. On one hand, STP cable has shielding material. This cable designs raise the cost of STP cable. On the other hand, during installation, an STP solution will take longer to terminate jack modules and properly bond the structured cabling system as the shielding makes this cable heavier and more difficult to bend or manipulate. That will add a little more to the installation cost.

Conclusion

From the above content, it shows that the main advantage of using an STP cabling system is the superior alien crosstalk. And UTP cable is simpler to install, quicker to terminate and less expensive than STP cable as to the material and installation costs. But for most installers and contractors, they are more familiar with UTP cable.

So which one will you choose for your 10GBASE-T network? If performance is the key driver, you are recommended to select an STP cabling system. Because STP has excellent alien crosstalk for 10GBASE-T application and eliminates the need to perform time-consuming field-testing for alien crosstalk. If you concern about bonding and grounding practices within the network, maintaining the integrity and continuity and grounded system over the lifespan of the cabling system, and want low-cost 10GBASE-T system, you are suggested to select a UTP cabling system.

Source: http://www.fs.com/guidance-to-choose-shielded-or-unshielded-cabling-for-10gbase-t-network-aid-489.html

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