[AusNOG] Lightning and FTTC - is it really this bad?

Paul Jones paul at pauljones.id.au
Thu Jan 21 12:29:47 EST 2021

> -----Original Message-----
> From: AusNOG <ausnog-bounces at lists.ausnog.net> On Behalf Of Karl Auer
> Sent: Thursday, 21 January 2021 11:24 AM
> To: ausnog at ausnog.net <ausnog at lists.ausnog.net>
> Subject: Re: [AusNOG] Lightning and FTTC - is it really this bad?
> There are two ways in to the CPE - the FTTC connection and the power
> supply to the CPE.
> The FTTC connections are themselves powered at the curb, and so may be a
> conduit for spikes into CPE.
> The likelihood of the cable run from the curb to the CPE getting hit directly is
> probably very low, but the likelihood of the power grid getting hit and
> sending a spike down the line to either the curb equipment and thence to
> the CPE or to the CPE directly is unchanged.
> Actually it's probably higher, given the greater number of powered devices in
> the network.

I would think a direct hit would generally let the smoke out, and then some. Just the EM fields from a nearby strike is enough to damage poorly designed equipment connected to long wires. You should see how much extra protection is provided in something as simple as an alarm system used in tropical storm locations (like Taiwan). Things like spark gaps and spike adsorbers.
I'm guessing the designers of the CPE made the same assumption we all did - the copper is not as long so the problem won't be as bad (i.e. save money on protection that is normally used when connecting to phone lines).


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