Asuming they are using some time domain reflectometry technique, I would assume that it could be done on a live comms cable. 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. Mark __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>