Tag Archives: STP

Cable Shielding of Shielded Twisted Pair

For the purpose of providing a reliable connection between electronic devices, choosing a proper shielded twisted pair cable is essential to the network using copper cables. EMI (electromagnetic interference) is a disturbance in twisted pair cables. It affects the performance of an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. But with the help of cable shielding, cables can be immune to the disturbance and keep a stable connection. And this article will present some knowledge about cable shielding. Hope you can find it useful.

STP vs. UTP

Before getting to know cable shielding, you may wonder about the real difference between shielded twisted pair (STP) and unshielded twisted pair (UTP). As their names suggest, STP has a shield that works as a guard and drains the induced current surges to earth. Yet UTP has no cable shield with such a function. But the shortcoming of STP cables is the extra shielding cost added to an installation. Typically, STP cables are more expensive than UTP cables. And due to the stiffer and heavier shielding, coping with STP cables is more difficult. But if you pursue a higher performance, STP will be a preferable choice.

Types of Shields

There are mainly two types of shields: braided shield and foiled shield. Braided shield is made up of woven mesh of bare or tinned copper wires. It has better conductivity than aluminum and more bulk for conducting noise. An easier attachment with connectors can be achieved by crimping and soldering the braid. However, braided shield does not possess 100% coverage. It usually provides 70% to 95% coverage according to the tightness of weave. But as a matter of fact, 70% coverage is always sufficient if cables are fixed. Another shielding is foiled shield. This type of shielding uses a thin layer of aluminum and has a 100% coverage around the conductors. But the drawback is that its conductivity is lower than copper braided shield.

shielded twisted pair

Different Constructions of Shielding

Today, people will use acronyms to name different shielding constructions. Take U/FTP as an example, the first letter “U” represents the outer shield or overall shield of cable, and the followed letter “F” represents the individual shield under the overall shield of each twisted pair or quad.

shielding-construction

Here are some commonly used shielding constructions:

1) Individual Shield

U/FTP is the typical individual shielding using aluminum foil. This kind of construction has one shield for each twisted pair or quad above the conductor and insulation. Individual shield especially protects neighboring pairs from crosstalk.

2) Overall Shield

F/UTP, S/UTP, and SF/UTP are overall shielding with different shield materials. Overall shield refers to the entire coverage around the whole cable. This type of shielding helps prevent EMI from entering or exiting the cable.

3) Individual and Overall Shield

F/FTP, S/FTP, and SF/FTP are individual and overall shield. This type of construction has both layers of shielding. And its immunity to EMI disturbance is greatly improved.

Meanings of the abbreviated letters:
U = unshielded
F = foiled shielding
S = braided shielding
TP = twisted pair

Applications

As for the application in 10GBASE-T Ethernet, UTP, U/FTP, F/UTP, F/FTP and S/FTP are often used. But their practicable cable categories are varied from cat 6/6a to cat 7/7a. When twisted pair cable is deployed for 40GBASE-T Ethernet, U/FTP, F/UTP, F/FTP, S/FTP are applied under cat 8/8.1/8.2.

Conclusion

Adopting shielded twisted pair cable is an effective method to prevent EMI from interfering signal transmission. And there are different shielding constructions for you to choose. Of course, using twisted pair without cable shielding is also feasible if your budget is limited. Wish you find the most suitable shielded twisted pair cable for your project!

Related Article:

Why Choose the Shielded Cabling System

How To Purchase Twisted Pair Cable

Twisted Pair Copper Cable — A Preferred Cable in Building Wiring

In recent years, as the demand for fast-speed and mass media is increasing, optical fiber cable shows an absolute advantage over copper cable. After fiber-to-the-home solved the “last mile problem”, there even emerged a sentence “optic fiber in, and copper wire out” on the Internet. However, is copper cable really useless? The answer is definitely No! Indeed, twisted pair copper cable has many advantages over optical fiber in the application of building wiring.

The most commonly used copper network cable in the horizontal wiring between buildings is twisted pair copper cable. Therefore, in this text, I will illustrate why twisted pair copper cable is a preferred cable in building wiring.

What is Twisted Pair Copper Cable?

A twisted pair cable is a pair of copper wires, with diameters of 0.4 -0.8mm , twisted together and wrapped with a plastic coating. The twisting increases the electrical noise immunity, and reduces the Bit Error Rate (BER) of the data transmission.

Types of Twisted Pair Cables

Classified by the inner structure of twisted pair copper cable, it can be divided into Unshielded Twisted Pair (UTP) and Shielded Twisted Pair (STP).

  • UTP is just two insulated pair twisted together. The EIA/TIA (Electronic Industry Association/Telecommunication Industry Association) has established standards of UTP and rated 6 categories of wire.
  • STP is heavier and more difficult to manufacture, but it can greatly improve the signaling rate in a given transmission scheme. STP is commonly used by large scale companies in high-end applications that require the maximum bandwidth.

The UTP and STP are showed in the picture below.

twisted pair copper cable

The difference between UTP and STP are stated below:

  • STP cables are shielded while UTP cables are unshielded
  • STP cables are more immune to interference and noise than UTP cables
  • STP cables are better at maximizing bandwidth compared to UTP cables
  • STP cable cost more per meter compared to UTP cables
  • STP cables are heavier per meter compared to UTP cables
  • UTP cables are more prevalent in SOHO networks while STP is used in more high-end applications.

For most common uses, it does not really matter whether you use STP or UTP as both would probably perform well. UTP is the more logical choice for the majority of enterprises in LAN as it is cheaper and much easier to find.

The Advantages of Twisted Pair Cooper Cables in Building Wiring

In the building wiring project, as the physical space of wiring is relevantly spacious, there is no need to worry too much about the wiring density. Therefore, though the diameter of copper wire is larger than optical fiber, there has enough space for the copper wire. And because of the large space, the problem of heat dissipation of copper wires is solved. The distance between enterprise buildings is relevantly short, therefore, even though the attenuation of copper wires is bigger than optical fibers, the influence on the whole network is small. What’s more, the port energy consumption has lower degree of influence on building wiring compared with data center. Therefore, the factors to be considered in the building wiring system inclined to the total cost of the project.

Compared with fiber optic network device, copper cable network device has an obvious advantage over the cost. Therefore, the copper twisted pair wiring system will remain the first choice in a fairly long period of time.

Besides the easy implementation and lower cost, twisted pair copper cable has other strengths:

  • High utilization of cables.
    If a portion of a twisted pair cable is damaged, it does not affect the entire network.
  • Anti-interference.
    Twisted pair cable can effectively restrain common mode interference. Even under the strong interference environment, it can transmit very strong image signals.
  • High reliability.
    One of the biggest advantages of copper cable is reliability. Network reliability is usually measured by Bit Error Rate (BER). The BER of copper cable is usually lower than the industry standard.
Tips to Be Borne in Mind When Choosing UTPs

When choosing UTPs, you should remind that the tighter the twisting, the higher the supported transmission rate and the greater the cost per foot. More twists per inch means more linear feet of copper wire used to make up a cable run, and more copper means more money.

If you are considering to rewire your buildings, the twisted pair copper cable is a good choice for your short distance cable application.

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