[time-nuts] sub cables...and GBR

Bruce Griffiths bruce.griffiths at xtra.co.nz
Thu May 1 22:57:42 EDT 2008

Didier Juges wrote:
> Well, I am not sure I can tell much about how modern repeater power supplies
> are made because I do not believe the spec I got is public domain, but I can
> tell you it's a little more elaborate than a power resistor in series with a
> shunt regulator, unfortunately.
> They are apparently running more than a few watts of electronics at each
> repeater. Each repeater operates from about 200V input voltage nominal, so
> 10,000 volts can drive about 50 repeaters in that case. I have not read the
> spec in great details (we won't bid on it as it is commercial) but I will,
> to try to figure out how they keep the voltages balanced. That's about 200W
> of power for each node.
> Also, and this is absolutely not clear to me, but they want the full
> isolation (10,000 volts) between input side and output side of the DC/DC
> converters. If the repeater is composed of optical devices, even if they
> convert optical to electrical and back to optical, I do not see the need to
> electrically isolate the electronics from the power cable, as there should
> be no other return for ground currents.
> 10,000 volts isolation with 2,000,000 hours MTBF in a 0.6" high package is
> no piece of cake...
> Didier KO4BB

EDFAs may be phased out in favour of using 1/2 as many Raman amplifiers 
which have a larger bandwidth.
(EDFA bandwidth ~ 4THz, Raman bandwidth limited by the number of 
different wavelength counter propagating pump sources )


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