h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Of course, life is never simple

I don't remember everything we learnt about optical fibres in Physics, but I do remember that there are problems with light taking different paths...

For example, suppose one light beam is at quite an angle, and bounces off the sides every millimetre it travels... and another is practically in line with the fibre, and bounces off only every metre. The first is going to take longer to arrive... which is rather upsetting if you're trying to send a clear signal

I seem to remember that the layer of plastic/glass around the core has the effect of increasing the critical angle, which lets more of the high-angle light escape...

There was also something about letting the plastic/glass graduate slowly in refractive index, making everything take the same (curvy) path...

Anyway -- just rooting around in my memory ... nice article