[time-nuts] 10 MHz over optical fiber?

[Lux, James P]

> > 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.
> >



Presumably, you're using a maser because you need good stability over significant time spans (seconds or greater)? Then you probably need some way to compensate for the changes in propagation through the fiber.  That's what the JPL boxes do. They send signals both ways (I don't have it in front of me, but it's possible it's on the same fiber, or at the least, two fibers in close contact, so they're in the same environment) and measure the round trip time.