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Old 18-01-2008, 17:41   #35
altis
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Re: BT to offer 100Mbit broadband

Quote:
Originally Posted by Stuart C View Post
Fibre offers the same speed whether you are 2 metres or 200 miles away from the source..
Not true I'm afraid Stuart!

Optical fibres still suffer from attenuation and, more critically, dispersion like copper cable - it's just that it tends to be at higher data rates.

Multi-mode fibre - the sort most common - is good for 1Gbps for up to only about 500m or 2km at 100Mbps. More details here:
http://en.wikipedia.org/wiki/Multi-mode_fiber

For longer distances we use single-mode fibre which has less dispersion. The fibre and the interfaces are much more expensive but are good for some 10s of kilometers - but not 200 miles!

A bit more overview:
http://www.fiber-optics.info/articles/fiber-types.htm
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