Narrowband-wideband boundary-guided optimal DSCM partitioning for all-order PMD compensation in high symbol rate...

Digital subcarrier multiplexing (DSCM) decomposes a wideband signal into multiple subcarriers that can be processed independently, providing an effective approach to mitigate all-order polarization mode dispersion (PMD) in ultra-wideband systems. However, the subcarrier number is not always "the more, the better," an improper partition can even degrade system performance while increasing digital signal processing (DSP) burden. This paper therefore proposes an optimal subcarrier partitioning strategy that achieves a favorable trade-off between PMD compensation performance and DSP resource consumption. First, a normalized evaluation criterion is employed to establish a clear boundary between narrowband and wideband systems. Then, based on the above classification, semi-closed-form expressions are derived to characterize the relationship between the DSP complexity and the normalized PMD for subcarrier-partitioned wideband systems under a given system reliability confidence level. Finally, subcarrier partitioning strategies are developed for both tap-preset and tap-non-preset scenarios. The results confirm the effectiveness of the proposed strategy in both scenarios, showing that it not only guarantees PMD compensation performance but also reduces the DSP complexity in the PMD equalization module by more than 20% compared with ultra-wideband single-carrier systems, while exhibiting sufficient tolerance to other transmission impairments.