Polarization optical time-domain reflectometry for polarization mode-dispersion measurement

Polarization mode dispersion (PMD) in dispersion-shifted fibers presents an inherent limitation in ultralong-distance communications systems. The advent of multigigabit-per-second systems and CATV applications makes it imperative that a good measure of PMD be obtained during fiber manufacture. Several techniques for the measurement of short-length PMD in fibers are currently available.1 A typical spool of fiber, however, has PMD values that vary along the length owing to minor perturbations during fabrication. As a result, a short-length PMD measurement on a specific section of a fiber made by using any of the techniques does not provide a complete knowledge of the statistical spread of PMD over the entire length. In this paper we show that by modifying a commercial optical time-domain re- flectometer (OTDR) with a polarizer/analyzer pair, one can measure short-length PMD’s in fibers.