[159100] in North American Network Operators' Group
Re: Fiber only in DataCenters?
daemon@ATHENA.MIT.EDU (Owen DeLong)
Fri Dec 21 14:02:21 2012
From: Owen DeLong <owen@delong.com>
In-Reply-To: <CAK__KztDPAtPwEyg8NYTASXj0DQsBWqzNzN_Edr-PurOwnXT5Q@mail.gmail.com>
Date: Fri, 21 Dec 2012 10:58:28 -0800
To: George Herbert <george.herbert@gmail.com>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Dec 21, 2012, at 10:54 , George Herbert <george.herbert@gmail.com> =
wrote:
> On Thu, Dec 20, 2012 at 3:20 PM, Matthew Kaufman <matthew@matthew.at> =
wrote:
>> On 12/17/2012 9:22 AM, joel jaeggli wrote:
>>>=20
>>> If the facility is big enough the utility of twisted pair becomes =
quite
>>> limited, both due to distance and differing electrical potential,
>>> multibuilding campuses in particular make this is a nonstarter.
>>=20
>>=20
>> For twisted-pair Ethernet: Distance yes. Differing electrical =
potential no.
>> It is a balanced pair, transformer coupled at both ends. As long as =
AC
>> common-mode pickup doesn't saturate the transformer core, it just =
works.
>=20
> ...Up to certain limits of DC / ground differential between the ends,
> at which one can cause sparks anyways.
>=20
> Yes, the POTS telcos use 48V in the same or lower quality wire pairs,
> and the various CatN wires should be able to take it, and the
> connectors. I'm not sure whether the sparks were from 110 or 220 V of
> differential, but I saw sparks.
>=20
Sparks come from voltage, but wire tolerance is entirely a matter of =
amperage.
A 24ga cat-6 wire can take millions of volts as long as you keep the =
amperage
low enough.
Owen
