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fiber questions

Garth

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anyone here upto speed with their fiberoptic cabling? got a few questions about fiber cable,
 

Garth

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i wanna know if there is a difference between multi function and single function cable? in actual performance, or just the amount of cable cores
 

cartoonwally

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I'm doing photonics atm at uni, hopefully i can help. I'm going to assume you mean single mode, multi mode.

Both of the cores are 'generally' the same for single mode and multi mode, usually 2 fibres, but multi mode tends to be a thicker.

The difference between the two is that multi mode (as the name suggests) can carry more than one wavelength of light at a time, and it is determined by the Q factor of the fiber. The same fibre can be converted into single mode if the wavelength goes over a certain wavelength, as determined by the Q factor.

Single mode is faster, and can go a lot further, yet is a lot more expensive than multimode fibre. Multimode is good for medium distance transmissions, not good for long distance because there tends to be more destructive interference as distance increases. I believe you'll find as we head towards the gigabit era that multimode will not be used as much, i don't think it can handle the new technology as well as single mode can.

Answer your questions?
 

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yes, i thought it was like that, but backwards, thought multimode was the good one over long distance, and single mode was good over shorter, learn something everyday, thanks guys, this is one electrican that is that little bit smater now
 

levymetal

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this image is really good to illustrate what happens as well (ignore the graded index):



in the multimode operation, you can see that the light bounces all around inside the fibre, so the total distance travelled by the light is increased thus the slower speed and shorter maximum distance. with the single mode it travels directly through the fibre maximising speed and distance.
 

tommo82

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I'm doing photonics atm at uni, hopefully i can help. I'm going to assume you mean single mode, multi mode.

Both of the cores are 'generally' the same for single mode and multi mode, usually 2 fibres, but multi mode tends to be a thicker.

The difference between the two is that multi mode (as the name suggests) can carry more than one wavelength of light at a time, and it is determined by the Q factor of the fiber. The same fibre can be converted into single mode if the wavelength goes over a certain wavelength, as determined by the Q factor.

Single mode is faster, and can go a lot further, yet is a lot more expensive than multimode fibre. Multimode is good for medium distance transmissions, not good for long distance because there tends to be more destructive interference as distance increases. I believe you'll find as we head towards the gigabit era that multimode will not be used as much, i don't think it can handle the new technology as well as single mode can.

Answer your questions?

Few corrections...

- A 'core' is 1 fibre strand, not a pair.

- Single mode fibre can carry multiple wavelengths (this is how WDM systems are constructed).

- multimode fibre is typically only used in buildings/campus. Realistic transmission range for modern protocols is about 500 metres.

- Most gigabit ethernet connections within a building use multimode fibre, not singlemode. MMF is easily capable of Gigabit and 10Gbps data rates and has been used in this fashion for around 10 years (for 1Gbps anyway).

In terms of what the original poster asked... you can get multi and single mode in any number of cores. typical values are 4, 12, 24, 44, 96, 144, 288 etc in a single cable.
 
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