Porn at 1Gbit / s.. nice 8)

I have a small collection of fiber cables that have been snagged, looped, crushed, bent and otherwise very mildly abused. Glass fiber is great for in cabinet connection, but even going between cabinets under the floor presents too much risk for me to be happy.

All hail our new masters, POF.

So, what happens if you use QAM on fiber?

Single and Multi-mode glass fibre is designed to carry digital light signals and as such has a very small core (as little as 10 micrometres in diameter). The fibre used by Siemens in this example has a vastly thicker core capable of transmitting analogue light signals, since QAM is an analogue modulation technique.

The cost of glass fibre with a core this thick would be far greater and probably not worth the effort. It also would probably not offer any great speed advantage. The distance that a signal would be able to travel before it becomes too attenuated, however, would be much greater than 100M.

I know you are presenting a simplified version, but please, you've made a rather sweeping statement by saying that QAM has 256 levels. Quadrature Amplitude Modulation can have as many amplitude/phase states in its constellation as is desired to balance phase noise vs data rate.

http://en.wikipedia.org/wiki/QAM#Digital_QAM

QAM is just a generalised description of a series of methods for modulation of data to analogue signals.

Bob

Unfortunately I don't think POF will offer any enhanced robustness over glass fibre: If you bend it past the recommended bend radius then you will still encounter reflection issues. Also, whilst it might not snap as catastrophically as glass, accidentally crushing, bending, treading on a plastic fibre may result in stressing of the plastic which will make the plastic go "cloudy" in the stress area and stop it working.

Tricky: You could use QAM on fibres in general, but there's not a lot of point as in practice it would increase noise in other modulation techniques and thus not offer any benefit.

Frequency Division Multiplexing is generally used when sending lots of data over a single-mode fibre, which means that you divide the frequencies available on the fibre into many channels and send data along each one. It's analagous to how they can send several TV channels over the same bit of space between the transmitter and your TV. You have a different data stream on each channel.