[time-nuts] Reverse isolation
bruce.griffiths at xtra.co.nz
Tue Mar 10 02:41:14 UTC 2009
Yes it is, and it can only usually be justified if one has an antenna
array to distribute low phase noise RF to.
One then also needs to add a means of compensating for fiber delay
tempco, which adds yet more cost.
A cleanup PLL using an ultra low noise OCXO locked to each photomixer
output is usually advisable as well.
Achieving more than about 120 dB of isolation at 10MHz is difficult
NIST claimed about 144dB of reverse isolation for one of their designs.
> All this sounds quite a bit more expensive and expansive than 3 ECL gates,
> even if one uses 3 packages to improve isolation...
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com
>> [mailto:time-nuts-bounces at febo.com] On Behalf Of Bruce Griffiths
>> Sent: Monday, March 09, 2009 9:08 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] Reverse isolation
>> A 10-1000mW of single mode ECDL helps.
>> But then you need a modulator.
>> You would also need to avoid frying any photomixer at the other end.
>> Didier wrote:
>>> But not necessarily lowest noise
>>>> -----Original Message-----
>>>> From: time-nuts-bounces at febo.com
>>>> [mailto:time-nuts-bounces at febo.com] On Behalf Of Don Latham
>>>> Sent: Sunday, March 08, 2009 8:48 PM
>>>> To: Discussion of precise time and frequency measurement
>>>> Subject: Re: [time-nuts] Reverse isolation
>>>> Best isolation is via a piece of fiber optics.
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