A2.3.2 Compare types of media for data transmission.
• Wired transmission via fibre optic cables and twisted pair cables; wireless transmission
• The advantages and disadvantages of these three types of data transmission
• Factors to consider must include bandwidth, complexity of installation, cost, range, susceptibility to interference, attenuation, reliability, security.
Big idea
Every network must convert bits into a physical signal that can travel from one device to another. The three dominant media are fibre-optic cable, twisted-pair copper cable, and wireless radio waves. Each embodies a characteristic trade-off among capacity, distance, cost, installation effort, resilience to noise, and the ease with which an attacker can intercept the signal. Choosing the appropriate medium therefore means balancing technical requirements with practical constraints.
Clear definitions
| Medium | Core physical principle | Typical use cases |
|---|---|---|
| Fibre-optic cable | Streams of light guided through a core of glass or plastic by total internal reflection. | Long-haul backbone links, data-centre interconnects, high-speed campus trunks. |
| Twisted-pair cable | Differential electrical signals carried on two insulated copper conductors twisted together to cancel electromagnetic noise. | Horizontal cabling to desktops, PoE devices, small office wiring. |
| Wireless (RF) | Electromagnetic waves radiated through free space; antennas convert between electrical signals and radio energy. | Wi-Fi LANs, mobile broadband, IoT sensor nets, point-to-multipoint links. |
Advantages and disadvantages
Fibre-optic
- Strengths: enormous bandwidth headroom (10 Gb/s to 400 Gb/s per wavelength, terabits with DWDM); immunity to electromagnetic interference (EMI); very low attenuation (<0.3 dB/km); difficult to tap without detection.
- Limitations: highest material and tooling cost; fragile to bending and pulling; installation requires skilled splicing, precise connectors, and specialised test gear.
Twisted-pair
- Strengths: inexpensive cable and connectors (Cat 5e/6/6A); easy field termination with simple tools; supports power-over-Ethernet (PoE); adequate bandwidth for 1–10 Gb/s up to 100 m.
- Limitations: susceptible to EMI and crosstalk despite twisting; attenuation increases sharply beyond 100 m; easier to tap than fibre; performance depends on cable category and quality of terminations.
Wireless
- Strengths: no physical cabling to the client—rapid deployment, flexible mobility, coverage of difficult terrain; installation cost concentrated in access points; scales to thousands of endpoints per AP.
- Limitations: bandwidth is shared and half-duplex; subject to interference (other WLANs, microwaves, Bluetooth), multipath fading, and regulatory power limits; range strongly affected by obstacles; highest interception risk—must rely on strong encryption.
Comparative overview of key factors
| Factor | Fibre-optic | Twisted-pair copper | Wireless radio |
|---|---|---|---|
| Bandwidth | 10 Gb/s – Tb/s per strand with wavelength-division multiplexing | 100 Mb/s – 10 Gb/s per link (Cat 5e–6A) | ≤ 1 Gb/s typical per AP (802.11ax up to 9.6 Gb/s shared) |
| Installation complexity | High: fusion splicing, precise end-faces, bend-radius control | Moderate: pull cable, crimp RJ-45, certify with simple tester | Low cabling overhead but requires site survey, AP placement, RF tuning |
| Cost (medium + labour) | Highest upfront; falling for short runs | Lowest per metre; low labour | Moderate hardware; low incremental user cost |
| Range without repeaters | Tens of kilometres with single-mode | 100 m per segment (90 m cable + 2×5 m patch) | 30–50 m indoors, hundreds outdoors line-of-sight |
| Susceptibility to interference | Immune to EMI and crosstalk | Moderate; twisting and shielding mitigate | High: co-channel users, household devices, weather |
| Attenuation | Very low (<0.3 dB/km) | Significant (≈ 22 dB/100 m @ 100 MHz, Cat 6) | High; path loss ∝ distance²–⁴ and obstacles |
| Reliability | Excellent if fibres protected; insensitive to lightning | Good; vulnerable to pinches, water ingress | Variable; depends on spectrum congestion and environment |
| Security (eavesdropping) | Difficult; tapping requires physical access and induces loss | Moderate; can be tapped with inductive couplers | Least secure: signal radiates; encryption essential |
Putting it in context
- Backbones and data-centre spines choose fibre-optic to meet extreme bandwidth and distance requirements while keeping electromagnetic noise and ground-loop problems at bay.
- Access switches to workstations or VoIP phones commonly use twisted-pair copper, trading some bandwidth ceiling for minimal cost, Power-over-Ethernet support, and ease of hand-tool termination.
- User mobility, IoT deployments, and temporary venues rely on wireless, accepting shared bandwidth and stringent security measures in exchange for zero–copper runs and rapid reconfiguration.
By understanding how each physical medium performs across bandwidth, cost, range, interference resistance, attenuation, reliability, and security, network engineers can blend fibre, copper, and wireless links to create a balanced, fit-for-purpose infrastructure.