Thunderstorms and FTTC

[Ardua]

For the last 2 hours, the West Midlands have been 'battered' by lightning, thunder and heavy rain. My connection has been steady on 80/20 for over a fortnight with a very low error count. Just checking the log, I see that at 9am (when we had frequent flashes of lightning), the error rate increased from 8 in the previous hour to 888 with a marked increase in downstream FEC errors. As the storms move north, the error rate is decreasing. Is FTTC less or more susceptible to weather factors than ADSL?

[Bill]

Is FTTC less or more susceptible to weather factors than ADSL?

The simple answer to that question is that, for a given length of cable, VDSL is more susceptible than ADSL to any external electromagnetic interference (including crosstalk) as it uses a much wider range of frequencies.

However, an FTTC connection is generally less susceptible than anything but a fairly short ADSL connection because the fibre segment isn't at all susceptible to this sort of interference, and FTTP would be almost completely immune.

It's the length of the copper bit that matters- an ADSL connection generally has a much longer aerial with which to pick up problems!

[Ardua]

Thanks Bill - interesting. Everything is back to normal now. At the worst of the storm, FECs were up to 900 over a 15 minute period. The FEC rate now is 0.13 per minute. I am on about 250 to 300 Metres of copper.

[Bill]

I'm about 450 metres from the cabinet, but the lack of a thunderstorm the same as yours ( ) at the same distance makes it difficult to say whether the figures are typical

One point is that, apart from confirming the presence of noise, FEC figures are to a large extent irrelevant- they're the errors that the modem could correct, it's the ones it can't correct that cause all the aggravation!

It does indicate that you've got some level of interleaving in use though, I don't think forward error correction is possible with pure fastpath.