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How do optical fibers use total internal reflection to guide light?

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A horizontal gradient bar displays the visible light spectrum from violet to red, labeled with corresponding frequency in terahertz, wavelength in nanometers, and photon energy in electron volts. — light When white light is spread apart by a prism or a diffraction grating, the colours of the visible spectrum appear. The colours vary according to their wavelengths. Violet has the highest frequencies and shortest wavelengths, and red has the lowest frequencies and the longest wavelengths.

Optical fibers utilize the principle of total internal reflection to guide light over long distances with minimal loss of intensity.12

An optical fiber consists of a central core surrounded by a layer of cladding, which is made of glass or plastic with a lower refractive index than the core. When light enters the core and strikes the interface between the core and the cladding at an angle of incidence greater than the critical angle, it cannot pass into the cladding. Instead, the light is completely reflected back into the core.32145

By repeatedly reflecting off this interface, light is effectively "piped" through the fiber, even when the fiber is curved. This mechanism allows for the efficient transmission of information via light pulses in fibre optics networks and enables medical imaging through devices like endoscopes, where bundles of fibers transmit light and images from inside the body.1452