Re: Now that's an odd failure mode...

[Chris Hartley <hartleyc () gmail com>]

At OARNet, the leading cause of aerial fiber outages was squirrels,
followed closely by weather, distantly by angry farmers and once in Akron,
random gunfire...  At OSU, the leading cause of fiber outages is squirrels,
followed distantly by fire.

Somewhere I have a great picture of a squirrel gnawing on a fiber that's
illuminated with a red visible laser.

Don't squirrels go back to their stash?  Could a squirrel get through that
hole, or were those just a lost stash?

On Fri, Jan 30, 2015 at 6:20 PM, Jay Hennigan <jay () west net> wrote:

> On 1/30/15 14:31, Larry Sheldon wrote:
>
> > The questions that have always intrigued me about the clip:
> >
> > Who made the hole and how long did it take (assumption is "woodpeckers
> > made it" but I have no idea how long it took to make the hole).)
>
> Most likely the woodpeckers, maybe helped by natural deterioration of
> the radome material or a defect in manufacture or installation or both.
>
> > HOW did they make it--seems like it would have been like making a hole
> > in a bass drum with a finger (lot of bounce, not much cut)?
>
> They pecked it. They can go pretty deeply into trees, and at the edge of
> the cover there wouldn't be much bounce.
>
> > How long did it take to put that many in, and how many worked on the
> > project?
>
> Unknown, but probably a long time, that's a lot of acorns!
>
> > Why didn't some alarm or path measurement disclose the deterioration
> > before the cavity was packed so full?
>
> I'm sure it did, over a period of months or years the signal strength
> would gradually go down as the dish filled up. No immediately obvious
> cause, this would be a real puzzler. There's typically a pretty good
> fade margin built in to such links, so it would be a very slowly
> decreasing RSSI coupled with likely a hockey-stick graph increase in BER
> as the dish got fuller. Depending on the RF frequency, could get worse
> with rain as the fade margin decreased. It may have been discovered
> accidentally if a tech happened to observe a bird while troubleshooting.
>
> Filling half the dish would be only a 3dB decrease, but once the acorns
> started to cover the feedhorn it probably got worse in a relative hurry.
> I have no idea of the dielectric properties of an acorn, it would
> probably vary depending on the moisture content and the RF wavelength
> relative to the size of the acorn. ;-)
>
> > Were the acorns cooked?
>
> Probably not. RF output likely a watt or two, spread out over a large
> area and several tens of thousands of acorns.
>
> --
> --
> Jay Hennigan - CCIE #7880 - Network Engineering - jay () impulse net
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