Random-Scrambling Tunable POTDR for Distributed Measurement of Cumulative PMD

We provide the theoretical framework for a new method of distributed measurement of cumulative PMD along single-mode optical fiber links. Independent pairs of optical pulses are launched into the fiber, where each pair consists of two pulses having the same state of polarization (SOP) but two different, closely spaced wavelengths. The key aspect is that both the SOP and center wavelength of a given pair need not be correlated with those of any other pair. This random-scrambling approach is well suited for an economically designed instrument that is more robust for field applications than previously reported approaches. Since no assumed model of the distributed birefringence behavior is required, the method is suitable for any actual single-mode telecom fiber span encompassing many fiber sections of different types and origins.