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-backreflected light along optical fibers in real time on the Poincare sphere. The first method, using Rayleigh-backscattered light, is here applied to measure the accumulation of polarization-mode dispersion (PMD) along an 11.5 km section of installed fiber link. With a simplified configuration, the second technique 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-reflections which arise from the fiber connectors that join the link