In most network installations the question of installing shielded or unshielded ethernet cabling cables comes up when planning logistics of a cable run and taking into consideration chances of electromagnetic interference (EMI). This type of interference is generated by electrical sources like powered devices and even other cabling. It is sometimes also referred to as radio frequency interference (RFI), noise, crosstalk, and alien crosstalk.
Electrical “noise” is virtually everywhere but in heavily concentrated environments like data and server rooms it can easily affect the performance of data transmission along an ethernet line.
It is standard for all ethernet cables to be constructed in “twisted pairs,” meaning the two conductors of a single circuit are twisted into a pair (4 pairs total for ethernet). This twisting already helps reduce environmental electrical interference, but you can add an extra layer of protection by installing shielded ethernet cabling.
The most popular means of shielding an ethernet cable is to add a layer of aluminum foil, tinned copper braid, or both materials around all four twisted pairs. This would be considered an overall shield. You can take this a step further by also wrapping each individually twisted pair in foil, braid, or both.
Let’s run through some of the varieties and characteristics of unshielded twisted pair and shielded twisted pair cabling to help cut through the noise of messy acronyms and better understand the construction of each cable type.
UTP: Unshielded Twisted Pairs
Entirely unshielded cabling is an inexpensive, lightweight, and flexible solution for ethernet runs or patch cabling. While there isn’t an added means of shielding to protect against EMI, UTP cables are inherently made with a twisted pair construction. The way these pairs are twisted already helps to block potential interference and reduce crosstalk.
With that said, UTP cabling is specific to the individual twisted pairs themselves not having any shielding around them, but you can still have a shielded ethernet cable with unshielded twisted pairs. This would add to the cost, but also increases protection against EMI without paying for additional shielding around each twisted pair.
F/UTP stands for Foiled w/ Unshielded Twisted Pairs. In this example, all four pairs are wrapped in an overall foil shield, while each individual pair is unshielded.
S/UTP stands for Shielded w/ Unshielded Twisted Pairs. Typically, this kind of cabling has only a braided shield around the four unshielded twisted pairs but is sometimes confused with other kinds of overall shielded ethernet cable. It’s always best to clarify the method of shielding when mentioning the style of shielding. It is also important to note that the braided shield allows for better grounding.
SF/UTP is Shielded and Foiled Unshielded Twisted Pairs which utilizes both a braided and overall foil shield around four unshielded twisted pairs. This would be the most effective means of eliminating crosstalk and providing ample grounding without paying the cost of having shielded twisted pairs.
FTP: Foiled Twisted Pairs
Shielded twisted pair cabling would be ideal in any environment where there are other powered devices, cabling, or electronics in the general vicinity of the run. Adding a layer of shielding around each twisted pair is an incredibly effective means at eliminating EMI/RFI and crosstalk. Just like the methods of overall shielding found in UTP cabling, aluminum foil and tinned copper braiding are wrapped around each pair denoting a STP assembly.
F/FTP stands for Foiled with Foiled Twisted pairs and has an overall foil shield in tandem with each individual twisted pair wrapped in its own foil shield.
S/FTP is Shielded with Foiled Twisted Pairs. This construction has the same double shielding, but the overall shield used is made up of a tinned copper braid with each individual twisted pair wrapped in foil.
SF/FTP denotes Shielded and Foiled with Foiled Twisted Pairs and provides the most protection from virtually all electronic interference. Each individual twisted pair is wrapped in foil, then wrapped in an overall foil shield, which is then covered in a secondary overall tinned copper braided shield. Again, this braided shield allows for superior grounding.
If you need any additional help in deciphering different shielded versus unshielded ethernet assemblies, or advice on which cable construction to use in your installation, contact the NavePoint sales team at 888-505-1363.
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