Introduction to Data Transmission Media
When data travels across a network, it needs a medium , a physical or wireless channel through which signals can travel. Choosing the right medium is one of the most important decisions in network design, as it directly affects speed, reliability, cost, and security.
There are three main types of transmission media you need to know for IB Computer Science:
- Fibre optic cables , transmit data as pulses of light
- Twisted pair cables , transmit data as pulses of electricity
- Wireless transmission , transmits data as electromagnetic waves
Each has its own strengths and weaknesses, and the right choice depends on the specific requirements of the network.
A useful framework for comparing transmission media is to evaluate them across eight factors: bandwidth, installation complexity, cost, range, interference susceptibility, attenuation, reliability, and security. Memorise these eight , they are exactly what exam questions ask you to compare.
Fibre Optic Cables
Fibre optic cable: A transmission medium that uses pulses of light to carry data through thin strands of glass or plastic fibre. It offers extremely high bandwidth and low signal loss over long distances.
How it works: A light source (typically a laser or LED) at one end converts digital signals into rapid pulses of light. These pulses travel along the glass fibre through a process called total internal reflection, bouncing off the inner walls until they reach the receiver at the other end.
Key characteristics:
- Bandwidth: Extremely high , can support gigabits per second (Gbps), making it ideal for high-speed data transfer
- Installation complexity: High , requires specialised tools, skills, and careful handling of fragile glass fibres
- Cost: High initial/installation cost, but very low maintenance cost over time
- Range: Excellent for long-distance transmission with minimal signal degradation
- Interference susceptibility: Immune to electromagnetic interference (EMI) , because light signals are not affected by electrical fields
- Attenuation: Very low , signal strength is maintained well over long distances
- Reliability: Highly reliable with low latency
- Security: Very difficult to intercept without physically tapping the fibre, making it highly secure
Fibre optic cables are the preferred choice for backbone networks (the high-capacity core of the internet), undersea cables, and any environment with high data transmission demands or significant electromagnetic interference.
