I ment it like this:

Suppose you place 3 lamps in your house, and connect them to computers.

Each lamp is flickering on and off, or maybe even slighty stronger, slightly 
weaker, to encode information.

Because the light from the lamps could hit your detector at the same time, 
it becomes impossible to decode the information ?

Which bit of information came from which lamp ?

It is important to seperate the bits from information.

Otherwise you'll get a mixed signal and that's bad.

So the idea is to place detectors and different locations.

Because the distance to each lamp is different, the light will hit the 
different detectors at different times.

Then look for patterns or calculations to figure it out/seperate them.

Bye,
  Skybuck.