We experimentally verify the possibility of measuring the difference in effective refractive index between higher-order-modes using a phase-sensitive OTDR, indicating that it is possible to measure the average difference over long fiber spans.
Antoine Pierre François Jego, Titus Lupu
Hubert van den Bergh, Georges Wagnières, Matthieu Philippe Emmanuel Zellweger, Andreas Pitzschke, Manish Jain, Ying Xiao