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Optical fibres transmit signals using:
ARefraction at the core surface
BTotal internal reflection at the core-cladding interface — core has higher refractive index than cladding
CDiffraction in the cladding
DPolarisation of the signal
Answer & Solution
Correct answer: B. Total internal reflection at the core-cladding interface — core has higher refractive index than cladding
**Optical fibres**: a high-n **core** surrounded by lower-n **cladding**. Light entering the core at the right angle undergoes repeated **TIR at the core-cladding interface** → propagates along the length with very little loss (>95% transmission over 1 km in silica fibres).
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