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Optical fibre communication
Intermediate
Total internal reflection guides light pulses.
Light pulses travel along glass fibres by total internal reflection with losses of 0.2 dB/km. A single fibre carries terabits per second.
Undersea cables connect continents.
Dispersion limits speed over long distances.
In more detail
Optical fibres guide light by total internal reflection in a glass core surrounded by cladding with a lower refractive index. They carry huge amounts of data over long distances with low loss.
Real-world uses
- Internet backbones use optical fibres.
- Medical endoscopes use fibres to see inside the body.
- Internet data travels through optical fibres as pulses of light, which are guided by total internal reflection.
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Frequently asked questions
Why do fibres not leak light?
Total internal reflection keeps light inside the core as long as the angle is steep enough.
Why is fibre so efficient?
Low attenuation at near-infrared wavelengths allows signals to travel many kilometres.
Why does light stay inside a fibre?
It reflects off the boundary with the cladding at angles greater than the critical angle, so it is trapped in the core.
Related topics in AC Circuits & EM Waves
Antennas · Waveguides and transmission lines · Modulation (AM and FM) · Radar · Lasers in communication · Electromagnetic shielding