10Base-FL

From: Tothwolf <tothwolf_at_concentric.net>
Date: Fri Feb 8 20:25:05 2002

On Fri, 8 Feb 2002, Pete Turnbull wrote:

> The usual concern is not capacity -- if the school already has copper
> it probably is 10baseT or 10base2/10base5 which is the same speed as
> 10baseFL -- but safety.

Exactly.

> You're not supposed to run copper between buildings for two reasons.
> First is that they may not be grounded at the same potential; there
> could easily be a voltage difference between them. Even a small
> difference can cause damage to interfaces, though if they're working
> at present, presumably that's not serious in this case. Tiny
> differences just cause increased error rates. However, if there
> should ever be an earth fault on one building, all bets are off.
>
> Second reason is inductive pickup, or change in ground potential due
> to nearby lightning. Even coax picks that up rather well.

Right. The only reason copper was run between the three buildings was
cost. I did not have a source for transceivers or fiber, and the school
has no budget for the network as it is. The copper has been in a year and
a half or so, and works ok, but I still want to replace it.

> The cheapest way to do this is often to find a pair of hubs (like the
> 3Com Netbuilders or PSII range) which can take an extra transceiver
> module or two in the back. They're usually cheap, and the Fibre Link
> interfaces are very cheap because hardly anyone wants them. Standalone
> media converters, on the other hand, are much more expensive, even
> secondhand.

You wouldn't happen to know someone with 3-4 24 port units they would be
willing to give the school do you? Currently I've got a large number of 12
port 'AMP' brand hubs installed, since thats what I had access to when I
put the cable in. I did install halfway decent patch panels, so patching
in new equipment is very easy.

> Best way to buy the fibre for short runs (10-50 yards) is to buy patch
> leads from a trade supplier. Trade suppliers are typically 1/2 - 1/8
> the price of end-user catalogues. Better still, sometimes you find
> people with surplus patch leads with ST connectors, which they've
> replaced with SC or even MT-RJ.

Thats what I had in mind. The condits are dedicated for network cable, so
I can use the existing copper to pull in fiber and or a new pull rope.

-Toth
Received on Fri Feb 08 2002 - 20:25:05 GMT