Measurement Based Modeling of Mode Coupling Effects in a 50 μm Graded Index Multi Mode Fiber

Abstract:
In mode division multiplexed transmission lines the amount of power coupled from one mode to another increases with the transmission length. Short lines can operate below the region of strong coupling. Especially here an accurate model of the impact of linear mode coupling is necessary. In recent years the influence of different perturbation effects onto the amount of mode coupling in multi mode fibers has been investigated qualitatively. However, there is still little quantified knowledge about which perturbation strengths are to be expected when links are built with real fibers. Consequently there is also a lack of information about the perturbation strength that should be assumed when attempting to model a specific fiber link. In this work we aim to build a fully parameterized model of the signal propagation through a 50 µm graded index multi mode fiber. This fiber type has been used in recent mode division multiplexing transmission experiments. The basis for the determination of respective values of the parameters is a measured power transfer matrix of a 4.4 km long fiber. In order to match model predictions and measurement results concerning the strength of mode coupling we investigate the perturbation effects of rotation, offset and core ellipticity.