Degree of Polarization of Intercore Crosstalk in WC-MCF Systems With Different Skew-Symbol Rate Products

The degree of polarization (DOP) of the intercore crosstalk (ICXT) field and on-off keying (OOK) signal field in weakly-coupled multicore fiber (WC-MCFs) systems are investigated. The long-term DOP, the short-term DOP, measured in a short time interval by actual polarimeters, and the average short-term DOP, that integrates the variation of the short-term DOP of the ICXT field along time, are assessed experimentally and by numerical simulation. For the cases of practical interest, where the intercore skew-laser linewidth product is much smaller than one, the ICXT is strongly polarized with negligible fluctuations over time for skew-symbol rate products, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$|S_{nm}|\times R_{s}$</tex-math></inline-formula>, much smaller than one, i. e., when the relative time propagation delay between two cores is much shorter than the symbol period. For scenarios in which <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$|S_{nm}|\times R_{s}\gg 1$</tex-math></inline-formula>, the short-term DOP and average short-term DOP of the ICXT field decreases meaning that it is composed by a polarized and an unpolarized component. In this case, the short-term DOP of the ICXT field presents significant fluctuations over time leading to a ICXT field that may be weakly polarized. In all cases of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$|S_{nm}|\times R_{s}$</tex-math></inline-formula> assessed, the long-term DOP of the ICXT field tends rapidly to zero after an elapsed time of a few minutes. For all the tested cores, the DOP of the OOK signal is close to one and shows negligible fluctuations over time.