PSN-L Email List Message

Subject: Re: "Giant Seismometer"
From: D Collins dcollin@...........
Date: Wed, 27 Dec 2000 09:14:11 -0700

At 05:28 AM 12/27/00 , you wrote:
>John --
>I admire the creative process that thought this one up!!!
>I wonder, however, if there isn't a basic flaw in this
>plan.  I would expect that any such fiber optic cables are
>installed with generous numbers of expansion loops.  Thus,
>there would be very little variation in strain in conjuction
>with geological events.  However the following does not
>mention the mechanism which produces said strain so I may
>have missed the point here.

Yes, as an old fiber design engineer for the phone company, our general 
rule of thumb was to go about three manholes and put in a slack loop. This 
insured that ample cable would be available for re-splicing in the event of 
a dig-up or some other problem.  Fiber optic cables are the strongest 
digger attractor in the world 8<)



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Larry Cochrane <cochrane@..............>