Patent ID: 6724469
Filing Date: 2004-04-20
Classification: G01M

Abstract:
A method of measuring characteristics of an optical path comprising the steps of: transmitting a first series of polarized optical signal pulses into the path, each of the pulses having a length that is long compared with a beat length of the optical path and having a first state of polarization (SOP);transmitting at least a second series of pulses into the path, the pulses of said second series each having a length substantially equal to the length of the pulses of the first series but having a second state of polarization that differs significantly from the state of polarization of the pulses of said first series of pulses when the first and second states of polarization are represented on the PoincarÃ© sphere; measuring, and averaging over a prescribed period of time, intensity of backscattered light corresponding to each of the first and second series of pulses; deriving, from said intensity measurements, a degree of polarization (DOP) signature comprising a degree of polarization with respect to distance along the path for each of the first and second states of polarization; and analyzing said DOP signatures to determine variations in polarization mode dispersion (PMD) along the length of the path.