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.