[time-nuts] Optical link connects atomic clocks over 1400 km of fibre

[Magnus Danielson]

Don't over-interpret the 50 Hz aspect, I don't remember those details 
from 4.5 months back or so, as I already indicated. I can ask on the 
details tomorrow. I think they discussed the Kerr effect:
https://en.wikipedia.org/wiki/Kerr_effect
The PTB folks asked me the same question essentially.

Would be nice to verify it.

Cheers,
Magnus

On 08/24/2016 12:11 AM, David wrote:
> I could not find it in the links but Magnus mentions 50 Hz instead of
> 100 Hz.
>
> I would expect a 100 Hz noise signal if it was vibration coupled from
> magnetostriction in a transformer; magnetostrictive strain depends on
> the magnitude of the magnetic field strength and not the sign which is
> why 50/60 Hz transformers hum at 100/120 Hz.  50 Hz however fits with
> piezomagnetism if the optical fiber was in an oscillating magnetic
> field and antiferromagnetic; for piezomagnetism, the strain does
> follow the sign.
>
> https://en.wikipedia.org/wiki/Magnetostriction
> https://en.wikipedia.org/wiki/Piezomagnetism
>
> I do not know if optical fibers are even slightly antiferromagnetic
> but maybe doping can make them susceptible?
>
> On Wed, 24 Aug 2016 09:31:57 +1200, you wrote:
>
>> What is the coupling mechanism giving rise to the 50Hz disturbance?
>> DaveB, NZ
>>
>> ----- Original Message -----
>> From: "Magnus Danielson" <magnus at rubidium.dyndns.org>
>> To: <time-nuts at febo.com>
>> Cc: <magnus at rubidium.se>
>> Sent: Wednesday, August 24, 2016 8:54 AM
>> Subject: Re: [time-nuts] Optical link connects atomic clocks over 1400 km of
>> fibre
>>
>>> ...
>>>
>>> These links is in principle not very complex, but they are regardless
>>> somewhat sensitive. One link experienced excessive 50 Hz disturbance,
>>> which they could trace to the fact that for a short distance the fibre was
>>> laying alongside the house 400V three-phase feed-cable with quite a bit of
>>> current in it.
>>>
>>> ...
>>>
>>> Cheers,
>>> Magnus
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>