[time-nuts] 10 MHz over optical fiber?

Didier didier at cox.net
Wed Nov 26 19:38:22 EST 2008


If your concern is simply a stable frequency reference, that's true, even
though I am not sure what kind of cleanup oscillator would match the short
term stability of a maser. But also if you want to use it as a time
standard, the phase shift in the fiber has to be compensated, and it's
variations over temperature/humidity/gravity and whatnot must be accounted
for.

This is time-nuts, we don't simply want to make things work, we want to make
them work good :-)

Didier

> -----Original Message-----
> From: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] On Behalf Of tomknox at nist.gov
> Sent: Wednesday, November 26, 2008 2:50 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] 10 MHz over optical fiber?
> 
> Hi Group;
> It seems to me that the increase in noise introduced with an 
> optoelectronic device would not matter in most applications 
> if a cleanup oscillator is added.
> 
> Best Wishes;
> Thomas Knox
> NIST
> 4475 Whitney Place
> Boulder Colorado 80305
> 1-303-554-0307
> tomknox at nist.gov
> 
> 
> 
> Quoting "Paul Boven" <p.boven at xs4all.nl>:
> 
> > Hi everyone,
> >
> > In message <20081124152247.DCDB0E91529 at mail.ebirds.it>, 
> Marco IK1ODO 
> > -2
> > writes:
> >> Hi all,
> >>
> >> I have to carry a 10 MHz standard frequency signal inside an EMC 
> >> screened room via fiber optic cable.
> >>
> >> Not willing to re-invent the wheel, do something like an optical 
> >> standard frequency link exist on the market?
> >> I think it is possible to use standard 100MB LAN transceivers, and 
> >> POF. Phase noise requirements are not very stringent, and the 
> >> distance is in the order of some tens of meters.
> >
> > I'm looking into something similar: transmitting an H-Maser signal 
> > (probably 10MHz) over some 34km using CWDM SFPs. At first 
> glance this 
> > seems fairly uncomplicated: get some SFPs, and SFP 
> connector + cage. 
> > Use a fast opamp/differential driver to drive the transmitting SFP, 
> > and use a similar setup at the other end to transform the received 
> > data back to 50 ohm unbalanced. How feasible would such a setup be?
> > Possible problems might be that a 10MHz squarewave is 
> simply too 'slow'
> > to be transmitted by an SFP, which expects 1.25Gb/s 8/10 
> encoded data.
> > Another interesting question would be how much jitter/noise such a 
> > setup would add?
> >
> > Regards, Paul Boven.
> >
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> 
> 
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