The Relation Between RSOP and PSP Rotation Rates and an Effective Algorithm for Monitoring PSP Rotation

We begin by theoretically analyzing the relationship between the rotation rates of the rotation of state of polarization (RSOP) and the principal state of polarization (PSP) in a fiber link where both polarization mode dispersion (PMD) and time-varying RSOP are present. The theoretical analysis is validated through numerical simulations. Our findings reveal that the rotation rates of both the input and output PSPs significantly differ from the channel’s RSOP rate in most scenarios. Moreover, under varying RSOP distribution scenarios within the channel, the relationships among the rotation rates of input PSP, output PSP and RSOP also differ, and therefore rotation rates of input or output PSPs can reflect the changes of RSOP, indicating that monitoring PSP rotation rate can enable a better understanding of RSOP. Furthermore, we propose a DSP-based algorithm for monitoring PSPs and their rotation rates. By jointly applying a sliding-window median filter and a modulus judgment procedure, the algorithm yields more accurate PSP trajectories and rotation rate estimates than the existing approaches in literature, while relying solely on the existing DSP module without requiring any additional hardware. The recovered PSP orientation and rotation rate information can then be fed into the CMA equalizer, enhancing its compensation performance and thereby improving the overall stability and performance of the coherent optical system.