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Why can fibre-optic glass carry signals over long distances with little loss of light?

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Fibre-optic glass is able to carry signals over long distances with minimal loss of light primarily due to the exceptional purity of the silica glass used in its construction and the physical principle of total internal reflection.12

The fibre consists of a central core surrounded by a cladding layer with a lower refractive index. This structural design ensures that light rays propagating within the core are reflected back into the interior at the core-cladding interface, effectively confining the light to the fibre.13

Furthermore, the development of high-performance fibres relies on extreme material purity. Early glass fibres were limited by impurities that caused significant light absorption; however, modern manufacturing processes produce silica fibres so transparent that light can travel over 100 kilometres with minimal attenuation. By utilizing specific infrared wavelengths where absorption is lowest, engineers can transmit signals across vast distances with high efficiency.12