PSN-L Email List Message

Subject: Re: fiber optic strainmeters
From: John Hernlund hernlund@............
Date: Thu, 28 Dec 2000 19:41:35 -0800

Mark Robinson wrote:

> Asuming they are using some time domain reflectometry technique, I would
> assume that it could be done on a live comms cable.

Apparently a special reflector has to be placed at one end of the line.  It

is a time-of-flight measurement that they are using.

> Fibre gyroscopes are popular on high end projects ... they measure
> rotation in accuracies of the order of the number of wavelengths around
> their circumference. they split the input light, the two signals going
> in opposite direction around a circle. the recombination of the light
> gives pulses with rotation ... I can't remember how they achieve
> quadrature.

For some reason that I am not aware of these guys have abandoned any kind
of interferometric technique.  Perhaps it is too expensive?  I understand
math and physics behind this stuff, but as far as the engineering end goes
I have no clue...

John Hernlund
Department of Earth and Space Sciences
University of California, Los Angeles


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