[time-nuts] Neutrinos not so fast? (defectove connector)

Magnus Danielson magnus at rubidium.dyndns.org
Thu Feb 23 01:10:28 UTC 2012


On 02/22/2012 11:26 PM, Poul-Henning Kamp wrote:
> In message<9A458DBA-3875-43B2-8383-5CA2F86BE8E2 at leapsecond.com>, "Tom Van Baak
>   (lab)" writes:
>
>> Could be on the electrical side of the adapter, not the optical
>> side. It's not impossible to get 60 ns of phase or trigger error
>> with RF connectors.
>
> I don't buy that explanation.
>
> It's very hard to get 60 ns *consistent* phase or trigger error,
> with any kind of connector, almost no matter how you go about it.

OTDR works just as normal TDR. If the fibre is not connected you get a 
reflection and not enough transmission. This is what you use OTDRs for.

I agree it needs more details to be believable.

> 20m of extra fiber sounds *much* more plausible.

60 ns is more like 12 m of fibre. SMF-28 has a refraction index of about 
1.45 depending on the wavelength of the laser. I use the rule of thumb 
that 1 ns is 3 dm in free air and 2 dm in coax and fibre, it's usually 
good enough for reality check calculations. Oh, and it's about 40 feet.

Anyway, I would like to see much more detailed description to see that 
it indeed was due to this error. Also I'd love to see it repeated such 
that one can see the time error go "on" and "off".

> Inventing an excuse about a loose connector to cover up the mistake
> sounds even more plausible.
>
> You really don't want to defend your phd dissertation, being known
> as the idiot who made a fool of both CERN and SanGrasso in one go.

This is science, making a spectacular error and then explain it in 
painstakingly detail can teach a lot more than a otherwise uneventful 
day at the lab, doing about the same measurement.

Learning something means better prepared to avoid it next time. 
Experience is being built.

Still don't know what really happened here, rumours at the best.

Cheers,
Magnus




More information about the Time-nuts_lists.febo.com mailing list