Fibre speed vs distance

Bill · Oct 10, 2010, 17:24:56

Quote from: Rik on Oct 10, 2010, 17:18:18
My measure of mismatch, Bill, is when I can't get my trousers on.

The usual meaning of VSWR is Voltage Standing Wave Ratio, I suppose it could stand for Very Stretchy Waist Restraint

Rik · Oct 10, 2010, 17:26:16

I like very stretchy.

esh · Oct 11, 2010, 13:15:43

How do I find my nearest green box without hiring a helicopter?

Any suggestions?

Rik · Oct 11, 2010, 13:20:42

Ask a BT engineer if you see one is about the only way I know, esh. I'm lucky, because mine just at the top of the road, and I've seen BT working there.

Technical Ben · Oct 11, 2010, 16:37:58

Quote from: Bill on Oct 10, 2010, 16:17:17
'Fraid not. From your link:
My bold.

In an isolated conductor, electricity travels at the same speed ("c", approx 3 x 10⁸ m.sec^-1), in a cable it travels slower. If I remember my transmission line theory, typical values vary from about 0.7c in coax to ~0.9c in a flat pair.

In a fibre optic, the light travels at c divided by the refractive index of the glass, so typically about 0.7c

Your right.

So, is it the fact that light is refracted (and so has longer to travel) that slows it down?

jm_paulin · Oct 11, 2010, 17:03:02

Quote from: Technical Ben on Oct 11, 2010, 16:37:58
So, is it the fact that light is refracted (and so has longer to travel) that slows it down?

Albert said: c is always c, regardless of your speed or anything else.
The killer was: The distance between A and B, that is in fact close to infinity....

I then switch to a logic course... when they taught me: 1 + 1 = 1

Technical Ben · Oct 11, 2010, 20:19:02

Well, you know we are all moving at C right? The only difference is how directly we move to each point. So if you feel your going round in circles you are! (Well, your atoms are anyhow)

alexwright · Oct 20, 2010, 22:29:06

Quote from: Technical Ben on Oct 11, 2010, 16:37:58
Your right.
So, is it the fact that light is refracted (and so has longer to travel) that slows it down?

No, it is due to light being a wave. The material a wave has to travel through makes a difference to the maximum velocity achievable.

Light can slow down to almost pedestrian speeds in the right material. See this link

There is also a type of radiation given off when electrons move faster than the local speed of light:
Cherenkov Radiation
The energy released slows them down to the local speed of light for the medium they are travelling through.

Rik · Oct 21, 2010, 11:25:04

I feel like I'm sitting in a physics class here. Thanks for all the technical background guys.