- Asked 2/20
- 2076 Bhadra · 2+5 marks
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Fibre uses; pros and cons over metal wire
Short answer
Optical fibres are widely used in telecom backbones, submarine cables, FTTH, LANs, and CATV. Advantages over copper: huge bandwidth, low loss (0.2 dB/km), EMI immunity, electrical isolation, light weight, security. Disadvantages: higher installation cost, fragility, difficult joining, and no power feeding.
Where are optical fibres most widely used? Explain the various advantages and disadvantages of optical fibers over metal wire communication.
Where optical fibres are used
Optical fibres are used most widely in telecommunication networks: long-distance and international trunk links, submarine cables, national backbones (e.g. the optical fibre backbone of Nepal Telecom and NEA), mobile tower backhaul, and fibre-to-the-home (FTTH) internet. Other uses are LANs and data centres, cable TV, military and aircraft systems (EMI immunity), medical endoscopes, industrial sensors, and illumination.
Advantages over metal wire communication
| Advantage over copper wire | Reason |
|---|---|
| Huge bandwidth | Optical carrier ~200 THz; Tb/s on one fibre |
| Low loss | ~0.2 dB/km, repeaters every 80–100 km (copper: ~2 km) |
| Immune to EMI and crosstalk | Light is not affected by electrical noise or lightning |
| Electrical isolation | Glass is an insulator; no ground loops or sparks |
| Small size, light weight | Fibre is ~125 µm; a cable is much lighter than copper |
| Signal security | No radiation; tapping is hard to do undetected |
| Raw material | Silica (sand) is plentiful; copper is costly |
| Long life, corrosion-free | Glass does not corrode |
Disadvantages compared to metal wire
| Disadvantage | Reason |
|---|---|
| Costly installation | Fusion splicers, OTDR and skilled staff needed |
| Fragile | Glass breaks if bent tightly or crushed |
| Difficult joining | Micron-level alignment for splices/connectors |
| No power feeding | Cannot carry DC power to repeaters/terminals like copper |
| Optical–electrical conversion | Extra transmitter and receiver circuits needed |
| Repair is harder | Locating and fixing a cut needs special tools |
Overall, the very high bandwidth and low loss make fibre the preferred medium for backbones, while copper remains useful for short drops and for carrying power.
✓ Answer checked by Claude Opus 5.5 (high effort)
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