S/FTP (Shielded Foiled Twisted Pair)

What is S/FTP?

S/FTP (Shielded Foiled Twisted Pair) is a high-performance Ethernet cable design that combines:

• An overall braided screen (S) surrounding all pairs.
• Individual foil screens (FTP) surrounding each twisted pair.

This provides significantly greater protection against electromagnetic interference (EMI), radio frequency interference (RFI), and alien crosstalk than F/UTP or U/UTP cable designs.

S/FTP is commonly used in industrial environments, data centres, critical infrastructure, and high-performance networking applications where maximum EMC performance is required.

S/FTP Construction

Overall Braided Screen

• Tinned copper braid surrounding all four pairs.
• Provides excellent protection against low-frequency electromagnetic interference.
• Offers superior mechanical durability compared to foil-only screens.

Individually Foiled Pairs

• Each twisted pair is wrapped in its own foil screen.
• Reduces pair-to-pair interference.
• Improves high-frequency performance.

Drain Wire

• Typically includes one or more drain wires.
• Assists with maintaining screen continuity.
• Facilitates grounding and bonding during termination.

Why Use S/FTP?

Maximum EMI Protection

• Provides excellent resistance to external interference.

• Suitable for environments containing:

  • Variable speed drives
  • High-current switchgear
  • Motors
  • Generators
  • Radio equipment
  • Industrial automation systems

Excellent Alien Crosstalk Performance

• Individual pair shielding significantly reduces interference between pairs.
• Particularly beneficial for high-speed Ethernet applications.

Improved Signal Integrity

• Helps maintain performance in electrically noisy environments.
• Reduces susceptibility to transient electrical disturbances.

Supports High-Speed Ethernet

• Commonly used for Cat6A, Cat7 and Cat8 cabling systems.
• Suitable for demanding 10 Gigabit Ethernet installations.

S/FTP vs Other Cable Types

Advantages of S/FTP

Exceptional EMC Performance

• One of the most effective copper cable screening methods available.
• Suitable for environments where standard Ethernet cable may experience interference.

Reduced Pair-to-Pair Crosstalk

• Individual pair screens improve isolation between pairs.
• Supports higher bandwidth transmission.

Excellent Mechanical Protection

• Braided screens provide additional physical robustness compared to foil-only designs.

Future-Proof Infrastructure

• Frequently specified for installations expected to support future network upgrades.

Limitations of S/FTP

Higher Cost

• More expensive than U/UTP and F/UTP cable.

Larger Diameter

• Typically thicker and less flexible.
• Requires larger containment and bend radii.

More Complex Termination

• Individual pair foils and braided screens increase termination time.
• Greater risk of poor workmanship if installers lack experience.

Grounding Requirements

• Proper bonding and earthing practices become increasingly important.

Screen Termination Requirements

Maintaining Screen Continuity

To achieve the intended EMC performance:

• Use screened patch panels.
• Use screened keystone modules.
• Use screened RJ45 connectors.
• Ensure braid and foil screens remain continuous through the channel.

Failure to maintain continuity can significantly reduce screening effectiveness.

Functional Earthing

The overall screen should be connected to an appropriate Functional Earth (FE) through the structured cabling infrastructure.

This provides a path for induced electrical noise and improves EMC performance.

Common Applications

Industrial Networks

• Manufacturing plants
• Utilities infrastructure
• Process control systems
• SCADA networks

Critical Infrastructure

• Power generation facilities
• Water treatment plants
• Gas transmission sites
• Transport infrastructure

Data Centres

• High-density networking environments.
• High-speed switch-to-switch connections.

Security Systems

• Large-scale CCTV systems.
• External camera networks.
• Perimeter security infrastructure.

Broadcast and Communications Facilities

• Radio transmission sites.
• Television studios.
• Communications hubs.

Relevant Standards

ISO/IEC 11801

Defines S/FTP cable construction and performance classifications.

BS EN 50173

European structured cabling requirements.

BS EN 50310

Grounding and bonding requirements for ICT systems.

BS EN 50174

Installation practices for information technology cabling systems.

BS 6701:2016+A1:2017

Requirements for telecommunications cabling installations within buildings.

Installation Best Practices

1. Use Screened Components Throughout

• Screened cable should be matched with screened connectors and patch panels.
• Mixing screened and unscreened hardware reduces overall effectiveness.

2. Preserve Braid and Foil Integrity

• Avoid excessive removal of shielding during termination.
• Follow manufacturer stripping instructions.

3. Observe Bend Radius Requirements

• Larger cable diameters require careful handling.
• Avoid crushing or deforming the cable.

4. Follow Grounding and Bonding Requirements

• Ensure patch panels and cabinets are correctly bonded.
• Follow BS EN 50310 recommendations.

5. Certify the Installation

• Verify:

  • Wire map
  • Length
  • NEXT
  • Return loss
  • Alien crosstalk
  • Shield continuity

When Should S/FTP Be Used?

S/FTP provides some of the highest levels of electromagnetic interference protection available in copper Ethernet cabling. By combining an overall braided shield with individually screened pairs, it delivers excellent EMC performance, reduced crosstalk, and reliable operation in electrically challenging environments, making it a common choice for industrial, critical infrastructure, and high-performance networking applications.