Guided Transmission Media in Computer Networks: Cables and Fiber Optics

Explore the different types of guided transmission media used in computer networks, including twisted-pair cables, coaxial cables, and fiber-optic cables. This guide compares their characteristics, advantages, disadvantages, and typical applications.

Guided Transmission Media in Computer Networks

Introduction to Guided Media

Guided transmission media, also known as wired or bounded media, provide the physical pathways for data transmission in computer networks. Unlike wireless transmission, where signals travel through air or space, guided media confine signals to a physical cable or fiber. This offers advantages in terms of reliability and security but introduces limitations in flexibility and mobility.

Types of Guided Transmission Media

1. Twisted-Pair Cable

Twisted-pair cables consist of two copper wires twisted together. This twisting helps reduce electromagnetic interference (EMI) and crosstalk (interference between adjacent wire pairs). They're commonly used in telephone lines and local area networks (LANs).

Types of Twisted-Pair Cable:
  • Unshielded Twisted Pair (UTP): The most common type; relatively inexpensive and easy to install. Different categories (Cat 1-Cat 8) exist, with higher categories supporting faster data rates.
  • Shielded Twisted Pair (STP): Includes a metallic shield for better protection against EMI. More expensive and more difficult to install than UTP.
Advantages of Twisted-Pair Cable:
  • Cost-effective (especially UTP).
  • Easy to install (especially UTP).
  • Supports high speeds (depending on the category).
Disadvantages of Twisted-Pair Cable:
  • Susceptible to interference (especially UTP).
  • Limited range (signal weakens with distance).

2. Coaxial Cable

Coaxial cable has a central copper conductor surrounded by insulation, a metallic shield, and an outer jacket. The shield provides excellent protection against EMI. It's used in cable television networks and some older computer networks.

Types of Coaxial Cable Transmission:
  • Baseband: Transmits a single signal.
  • Broadband: Transmits multiple signals simultaneously.
Advantages of Coaxial Cable:
  • High bandwidth.
  • Good shielding against EMI.
Disadvantages of Coaxial Cable:
  • More expensive than twisted-pair cable.
  • A break in the cable can disrupt the entire network.

3. Fiber-Optic Cable

Fiber-optic cables transmit data using pulses of light. They offer extremely high bandwidth, low signal loss, and immunity to EMI, making them ideal for long-distance, high-speed communication.

Components of Fiber-Optic Cable:
  • Core: The central glass or plastic strand that carries the light.
  • Cladding: A layer surrounding the core that reflects light back into the core.
  • Jacket: A protective outer layer.
Advantages of Fiber-Optic Cable:
  • Very high bandwidth.
  • Excellent signal quality over long distances.
  • Immune to EMI.
  • Highly secure.

4. Connectors

Connectors are used to terminate and connect different segments of guided media. Examples include RJ-45 connectors for twisted-pair cables and BNC connectors for coaxial cables.

Applications of Guided Transmission Media

  • LANs: Twisted-pair and coaxial cables.
  • WANs: Fiber-optic cables.
  • Internet Backbones: High-capacity fiber optic cables.
  • Telecommunication Networks: Fiber optics.

Advantages of Guided Media

  • High reliability.
  • High security.
  • High bandwidth (especially fiber).
  • Resistance to interference.
  • Predictable performance.
  • Suitable for long distances (especially fiber).
  • Cost-effective for shorter distances (twisted-pair).

Disadvantages of Guided Media

  • Limited mobility.
  • Susceptible to physical damage.
  • High installation costs (for long distances).
  • Bandwidth limitations (for some types, like twisted-pair).
  • Requires physical infrastructure.
  • Environmental concerns related to manufacturing and disposal.

Conclusion

Guided transmission media are essential for building reliable and high-performance computer networks. Understanding their properties and limitations is crucial for designing and managing effective network infrastructures.