[time-nuts] sub cables

Poul-Henning Kamp phk at phk.freebsd.dk
Thu May 1 17:18:07 EDT 2008

In message <qsak149dee8iddn3u4826obrvtf0ssrpel at 4ax.com>, Neon John writes:

>Now I'm curious how power is tapped off at each repeater point.  I understand
>the daisychain architecture but I'm wondering about the details, what
>components can withstand the intial high voltage surge as the cable is
>charging and how the voltage drop at each repeater is maintained relatively
>constant, even if the repeater fails and quits consuming power.

It may be different these modern days, but it used to be that each
repeater had a (power)resistor connected in series with the supply
wires and the amplifier was connected across the resistor.

If the amplifier disconnected, the resistor kept continuity, if the
amplifier shorted, there would be continuity as well.

In addition the resistor kept the electronics from getting too cold.

>Also, is it true that an optical cable will keep working with a single
>repeater failure, that the laser light will pass through unamplified?  Seems
>like I read that somewhere but I'm not sure.

Yes, that's the major benefit from the "erbium doped fiber repeater"
design.  Google it for details.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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