- 2070 Chaitra · 4+3 marks
Fiber optic vs copper cable
Short answer
Fibre offers huge bandwidth, very low attenuation (0.2 dB/km at 1550 nm), immunity to EMI, no crosstalk, security, small size and electrical safety. Use fibre for backbone, submarine, FTTH, base-station backhaul, OPGW and high-EMI links. Use twisted pair for subscriber loops, DSL and short LANs, and coax for antenna feeders, cable TV and CCTV.
Describe briefly the advantages of fiber optic cable over the copper cable. Advise suitable application of both the media.
Optical fibre carries information as light pulses through a glass core by total internal reflection, while copper cable (twisted pair, coaxial) carries electrical signals. Fibre is now the main medium for backbone networks.
Advantages of fibre over copper
- Huge bandwidth – tens of GHz·km per fibre and terabit capacity with WDM, compared with a few hundred MHz on copper.
- Low attenuation – about 0.2 dB/km at 1550 nm, so repeater spacing of 80–100 km or more; copper needs repeaters every 1–2 km at high bit rates.
- Immunity to EMI/RFI – glass is non-conducting, so no electrical interference, lightning surge or ground-loop problems; can run beside power lines (e.g. OPGW on HV towers).
- No crosstalk – light does not leak into neighbouring fibres.
- Security – very hard to tap without detection; no radiation.
- Small size and weight – a thin cable holds many fibres; easier to install in ducts.
- Electrical isolation and safety – no sparks; usable in hazardous areas.
- Raw material – silica is abundant; no copper theft value.
- Long life – no corrosion.
Limitations: higher cost of terminal equipment (lasers, photodetectors), difficult splicing, fragile, and cannot carry power to remote equipment.
Suitable applications
| Medium | Suitable applications |
|---|---|
| Optical fibre | Inter-exchange trunks and national backbone (e.g. optical fibre along highways in Nepal), submarine and international cables, mobile base-station backhaul, FTTH internet, data-centre and LAN backbones, OPGW on power lines, links in high-EMI areas |
| Twisted pair copper | Subscriber telephone loops, DSL, Ethernet LAN up to 100 m, intercoms, low-speed control and alarm circuits |
| Coaxial copper | Antenna feeders, cable TV distribution, short high-frequency links between equipment, CCTV |
In short, fibre is used where distance, capacity or interference is the main issue, and copper where the distance is short, the data rate modest, power feeding is needed, or low cost of terminal equipment matters.
✓ Answer checked by Claude Opus 5.5 (high effort)
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