How does light travel down a fibre optic cable?

Many strands make light work...


Asked by: Harry Calder, Birmingham

At the core of the fibre optic cable is a strand of plastic or pure optical glass about 0.01mm in diameter. Surrounding it is a highly reflective cladding with a different refractive index to that of the core. The refractive indices of each material are engineered to ensure that light always reflects back off the cladding and is never absorbed by it, regardless of whether the cable is straight or bent round. It’s a bit like carrying a torch through a long winding tunnel lined with perfect mirrors.

Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.