Quote from Praveen Gupta on May 4, 2022, 1:53 AM

Theoretically, the light guide can be any medium that can guide light. Guiding implies transmission of light along the path of the guide. An optical fiber is one of the best light guides invented so far. Air is not a good light guide as it will allow light to disperse and scatter.

Glass pipes or plastic pipes are also good light guides. Specially designed light guides – the ones with a core region to launch the light and a cladding region to reflect back the escaping light – are efficient to guide the light without much transmission loss. Glass/Plastic pipes and tubes are used in the illumination and decoration industry.

Quote from Fiber on May 4, 2022, 1:54 AM

good explanation