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arXiv · 2502.13706

Closed-Loop Polarization Mode Dispersion Mitigation for Fibre-Optic Time and Frequency Transfer

Thomas Fordell·Anders E. Wallin·Thomas Lindvall·Kalle Hanhijärvi
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Abstract

A polarization switching pulse interleaver is shown to be effective in reducing timing noise due to polarization mode dispersion in time and frequency transfer based on mode-locked lasers and standard single-mode fibres. In closed-loop time transfer over a 30-km dispersion-compensated fibre link with 300~fs of differential group delay, polarization interleaving reduced the delay variations to <20fs. The results indicate that the remaining drift is caused by polarization-dependent loss and by AM-to-PM noise conversion in the photodiodes, suggesting the need for a "double-balanced" phase detector in the receiver, that is, a phase detector balanced in power and polarization. By mitigating the polarization dependence, this work demonstrates a simple approach that can potentially yield sub-femtosecond-level, long-term time transfer in long-haul fibre links utilizing standard single-mode fibres.

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Thomas Fordell, Anders E. Wallin, Thomas Lindvall, Kalle Hanhijärvi. 2025-02-19. Closed-Loop Polarization Mode Dispersion Mitigation for Fibre-Optic Time and Frequency Transfer. https://arxiv.org/abs/2502.13706

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