Polarisation OTDR measurements and theoretical analysis on fibres with twist and their implications for estimation of PMD

The authors present an analytical solution for the back scattered state of polarisation (SOP) from a uniformly linear birefringent fibre subject to elastic twist which shows that the twist significantly influences the periodicity of the observed signal from the polarisation optical time domain reflectometry (POTDR), and has to be taken into account when estimating polarisation mode dispersion (PMD) using this technique. Experimental results confirm the predictions.