> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Bruce Griffiths > Sent: Wednesday, November 26, 2008 6:56 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] 10 MHz over optical fiber? > > Didier wrote: > > 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 > > > > > Didier > > A linear temperature ramp will create a linear ramp > (equivalent to a frequency shift) in the fiber delay. > Such temperature ramps may be expected at least twice a day. > In other words the the rate of change of temperature needs to > be low to preserve the frequency accuracy at the receive end > of the fiber. > > Bruce >
Bruce, Over a 34 km path, one should expect temperature variations not to be uniform (unless the fiber is buried, but over 34 km, that would be expensive), so simple open loop pre-programmed compensation would probably not work well, some form of active, dynamic compensation should probably be used. Didier _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.