Why is using visible light for radio transmission not feasible?

[bsmith]

Homework Statement

Why can't you make radio transmitter that transmits visible light instead in the same way we transmith AM signals?

Homework Equations

The Attempt at a Solution

Im thinking maybe they would not be very effective as their wavelenth is so small, they would die out rapidly...

 

[AlephZero]

There are lots of practical devices that use AM visible or infra red light for data transmission. For example TV remote controls, infrared communications ports on PCs, etc.

There is no problem in principle with long distance transmission. For example we can detect the AM visible light signals from pulsars many light years away from earth. However short wavelengths do not diffract round large objects, so you can only communicate between devices that can "see" each other with no obstructions in between them.