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Cable Types and Standards

Jun 16, 2025

Overview

This lecture covers the differences between types of fiber optic and copper cables, industry standards, common issues like cross talk and attenuation, and best practices for installation and testing.

Fiber Optic Cables

  • There are two main types: multimode and single mode fiber.
  • Multimode fiber allows multiple light paths; common core sizes are 50Ξm and 62.5Ξm.
  • Single mode fiber uses a single light path with a smaller core size of about 9Ξm.
  • Both fiber types have 125Ξm cladding, making external size similar.
  • Mixing fiber types can cause communication errors.
  • Fiber types can sometimes be distinguished by color or labeling, but it's best to document and verify all fibers.

Copper Cables and Standards

  • Multiple copper cable types exist, standardized by the Telecommunications Industry Association (TIA).
  • Cables are categorized (e.g., Cat5, Cat6, Cat7), each supporting different speeds and standards.
  • Ethernet standards specify minimum cable categories and maximum distances (e.g., 1000BASE-T requires Cat5 up to 100m; 10GBASE-T requires Cat6 up to 55m).
  • Bandwidth is the theoretical max data rate; throughput is actual data over time.

Testing and Installation Best Practices

  • Always test installed cables to confirm proper operation and category compliance.
  • Using the wrong cable category can result in errors, slow performance, or signal loss.
  • UTP (Unshielded Twisted Pair) has no shielding; STP (Shielded Twisted Pair) uses shields to reduce interference.

Signal Interference and Cross Talk

  • Cross talk is interference between wire pairs, measured as NEXT (near end) and FEXT (far end).
  • Alien cross talk refers to interference from adjacent cables.
  • ACR (Attenuation to Cross Talk Ratio) compares signal loss to interference; higher ratios mean better signal quality.
  • Maintaining cable twists and proper connectors reduces cross talk.

Physical and Environmental Factors

  • EMI (Electromagnetic Interference) can affect cables; proper shielding and placement minimize this.
  • Avoid bending cables beyond their minimum radius and avoid staples or harsh cable ties.
  • Keep network cables away from power sources and interference-generating devices.

Cable Termination and Pinouts

  • Proper termination and matching wiring at both cable ends are critical for correct operation.
  • Pin mismatches or crossed pairs can reduce speeds or cause errors.
  • Some Ethernet chipsets can auto-correct crossed pairs (auto-MDIX), but not all do; proper wiring is always best.

Key Terms & Definitions

  • Multimode Fiber — Fiber optic cable allowing multiple light paths (modes).
  • Single Mode Fiber — Fiber optic cable allowing only a single light path.
  • Cladding — Outer optical layer surrounding the fiber core.
  • TIA — Organization that sets standards for cabling and connectors.
  • UTP (Unshielded Twisted Pair) — Cable with twisted wire pairs and no shielding.
  • STP (Shielded Twisted Pair) — Cable with shielding to prevent interference.
  • NEXT (Near End Cross Talk) — Signal interference measured at the transmitting end.
  • FEXT (Far End Cross Talk) — Signal interference at the receiving end.
  • ACR (Attenuation to Cross Talk Ratio) — Measure of signal loss versus interference.
  • Auto-MDIX — Technology that automatically corrects for crossed wires in network cables.

Action Items / Next Steps

  • Document and label all fiber and copper cables.
  • Test installed cables with a cable tester for correct terminations and category compliance.
  • Review installation practices to minimize interference and maintain cable integrity.

Full transcript