It is expected, that future passive optical networks (PONs) operating at 100 Gbit/s or beyond, will require coherent reception and higher order modulation both in the optical line terminal (OLT) and in the optical network units (ONUs). However, the ONU is a cost sensitive element and thus has to be based on low-cost DFB lasers, whose emission wavelength can vary within a certain range. In a time-division multiplexing (TDM) PON, each upstream burst will thus feature a different frequency offset. In this work, we discuss a coherent PON architecture based on a frequency-comb laser and study complexity-vs.-performance trade-offs for different data-aided and non-data-aided frequencyoffset estimation schemes.
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