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Why are silica glass and rare earth elements used in optical fibres?

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electron hole: movement — materials science Movement of an electron hole in a crystal lattice.

In materials science, silica glass and rare earth elements serve distinct, essential roles in the functionality of optical fibres.

Silica Glass
High-performance optical fibres are primarily manufactured from fused silica glass due to its extraordinary transparency, which allows light to travel over long distances with minimal loss of intensity. The fibre is structured with a core and a cladding, both made of dielectric materials with different refractive indices. This configuration enables total internal reflection, effectively confining light pulses within the core. By doping the silica with materials like fluorine or germanium, engineers can precisely modify the refractive index to optimize signal transmission and minimize dispersion.123

Rare Earth Elements
Rare earth elements, specifically erbium, are used to create optical amplifiers. In these devices, a short length of fibre is doped with erbium ions. When a signal passes through this section, the excited ions contribute photons to the light beam, amplifying the signal without the need to convert it into an electrical format. This technology is critical for maintaining signal strength in long-distance, transoceanic fibre-optic cables.4