🚀 go-pugleaf

In article <WINSTON.93Jan9123922@yuka.kuamp.kyoto-u.ac.jp> winston@kuamp.kyoto-u.ac.jp writes:
>
>What is the actual signal propagation delay in an FDDI fibre optic cable?
>Is it equal to the speed of light in free space, or is it a fraction of that?

It's my understanding that the velocity of propagation in any media
besides vacuum is lower than c. I've seen figures of .8+ c for fiber
cabling, but I think it's really up to the cable.

>Similarly, what is the signal propagation speed in a coaxial cable that is 
>used by the common LANs, such as, Ethernet and Token Bus?

Typical 10base5 VP is .77c. 10Base2=.66 c, 10BaseT=.58 c. This is the
main reason for different distance limitations, to compensate for
different delay budgets (10BaseT being a special case; you loose the
signal long before you exceed the delay budget in most cases).

Having a higher VP does not mean you have a faster LAN. A 10Mhz or
100Mhz signal rate is the same regardless of how fast it travels from
point A to point B. High VPs do grant you extra distance, though.
-- 
Rich Lawrence, Synoptics Systems Engineer  DOD#9630  rich@grebyn.com
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