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

[Bob kb8tq]

Hi

I would not rule out line noise into the electronic side of things.

Bob

> On Aug 23, 2016, at 7:06 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
> 
> 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
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