Polarization-mode dispersion measurements along installed optical fibers using gated backscattered light and a polarimeter

We describe two new techniques that utilize a polarimeter for studying the state of polarization of gated Rayleigh-backscattered or Fresnel-backreflec ted light along optical fibers in real time on the Poincare sphere. The fir st method, using Rayleigh-backscattered light, is here applied to measure t he accumulation of polarization-mode dispersion (PMD) along an 11.5 km sect ion of installed fiber link. With a simplified configuration, the second te chnique is developed and applied for measuring the PMD of individual fiber subsections in a 37 km long link, This is achieved by using the Fresnel-ref lections which arise from the fiber connectors that join the link.