Question regarding fibre optics.

Robert

Robert

Robert

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We had a "2-channel optical fibre system" demo'd to us at uni the other day. Now I'm really confused because I'm sure the guy said that the sound would be LOUDER over a 1km fibre cable than a 3m/1m. Also I seem to remember him saying the sound would be distorted over the 1m cable, but should be fine over the 3m cable - then sound much louder over the 1km cable. Now I can't find anything in my notes about it - nor on google. Well, saying that - I've found this tidbit:

"As mentioned above, some signal loss occurs when the light is transmitted through the fiber, especially over long distances (more than a half mile, or about 1 km) such as with undersea cables. Therefore, one or more optical regenerators is spliced along the cable to boost the degraded light signals. An optical regenerator consists of optical fibers with a special coating (doping). The doped portion is "pumped" with a laser. When the degraded signal comes into the doped coating, the energy from the laser allows the doped molecules to become lasers themselves. The doped molecules then emit a new, stronger light signal with the same characteristics as the incoming weak light signal. Basically, the regenerator is a laser amplifier for the incoming signal. See Photonics.com: Fiber Amplifiers for more details."


The thing is - is this built into ALL fibre cables over a certain lengths, or just specific ones? Also - the cables where raw cables - just both ends connected to the machinery (no in-between bits).
 
He used 1 kilometre line and a 1&3 metre size cables.

Doesn't really help mate. Why would it sound better and louder on the 1k line?

Edit: Shouldn't this be the other way round? The only thing I can think of is that the thing above which is spliced into the cable boosts the sound to a greater volume etc over a shorter cable - but why would the shorter cable produce a degraded sound?
 
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Basically the system produced music (connected to some cheap pc speakers). The music was transmitted over the optical cable. When the sound came out through the speakers over the 1km line - it was louder than the 3m/1m lines.

Picture.jpg


Here's a schematic of the circuit.
 
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Right - so the length of the cable means jack all? Argh! This was a MSC student doing this demo for us in a lab :(.

So the sound will be EXACTLY the same over all lengths?
 
Why do we get fed so much BS at uni. Half of my mates are writing their reports based on the fact that it apparently got "quieter" when using shorter cable compared to longer. Now thats gone out the window. We can't even contact the student to get more info as his e-mail addy expired and he won't give us his personal one.
 
It seems as though it is combined into one signal - converted to digital then changed back to analogue. At one point he turned the volume nob and it had no affect? The sound stayed at the same volume?
 
Yes. This is the point - but it's still confusing. When connected with the 1km cable, it was just louder - full stop. When connected via the 1m, it was noisey (interferance sound) and lower volume.

Hmm - the singal is only analogue at the start and end, weird. This shows why 35 people have complained about this lecturer.
 
The cables where all the same - he just said they were fibre optic - end of.

Wasn't meaning that, meant to include that somewhere about the lecturer :p. I've done a page so far of 5 - should get another 1-2 then I need to put this stuff in their somewhere, but the guy just wasn't clear. His english wasn't too good - maybe it was lost in translation somewhere :p.
 
Please mate. Basically what we were told I've blurted on here. The the guy WASN'T a lecturer - the lec who had us walked out after he took a register. I can't get hold of the guy as he doesn't have a set time to be IN and he wouldn't give us his OWN e-mail (his uni one expired). It's hardly surprising that this stuff is wrong as this guy didn't even know wireless networks existed :/

My hotmail addy is under my avatar.
 
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