[time-nuts] 10 MHz over optical fiber?

Scott Mace smace at intt.net
Tue Nov 25 19:42:07 UTC 2008


In looking at the off-the-shelf boxes, jitter seemed to vary from ps range
to tens of ns.  Also, how stable is the 34km of fiber...  One of the
manufacturers I looked at had a 1550nm option, so it's probably not a stretch
to get it on a 100GHz ITU grid channel or other CWDM channel.

	Scott

Paul Boven wrote:
> 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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