Assessing the Impacts of All-Order PMD on Fiber Communication Systems via a Unified Metric Scheme

Polarization mode dispersion (PMD) impacts optical fiber communication systems in both the time and frequency domains. Traditionally, mean differential group delay (DGD) and the average rotation of state of polarization (RSOP) have been used to assess the impact of PMD on systems. However, these metrics only capture the polarization information of the fiber channel, without accounting for aspects of the fiber communication system. This paper proposes a set of normalized polarization metrics, tied to the system's transmission symbol rate, to provide a more comprehensive assessment of PMD impairments. These metrics incorporate both polarization properties of the fiber channel and transmission characteristics of the system, providing a more accurate assessment of the impact of all-order PMD on optical fiber communication systems. The key features of the proposed normalized polarization metric assessment method include: (1) The symbol period of the transmitted signal is employed to normalize both the mean DGD and the average RSOP. (2) In contrast to regular autocorrelation functions (ACFs), the normalized time ACFs for RSOP and PMD, along with correlation symbol length, are introduced to determine how quickly or slowly RSOP and PMD vary over time. Additionally, the normalized freqn5uency ACF for PMD and the normalized correlation bandwidth are proposed to classify the transmission system as wideband or narrowband. (3) A normalized DGD map is introduced to visually depict the temporal and spectral effects of PMD on communication systems. (4) The proposed normalized polarization metric facilitates the optimal design of the key parameters of polarization equalization algorithm to prevent overprovision of receiver resources.