Nonlinear Cross-Polarization Mitigation Algorithm

The present document relates to optical transmission systems. In particular, the present document relates to methods and systems for the mitigation of Cross- Polarization Modulation (XPOLM) in optical transmission systems. A coherent optical receiver (200) adapted to receive an optical signal transmitted over an optical transmission channel exhibiting XPOLM is described. The received optical signal comprises a first polarization component and a second polarization component. The first and second polarization components comprise sequences of Mary phase shift keying, referred to as MPSK, symbols, respectively, M being an integer, with M > 2. The coherent optical receiver (200) comprises a conversion and processing unit (201, 202) adapted to generate a set of digital signals based on the received optical signal; a polarization de-multiplexing unit (203) adapted to demultiplex the set of digital signals into a first two dimensional, referred to as complex, component in a first polarization axis and a second complex component in a second polarization axis; and an XPOLM compensation unit (204) adapted to transform the first and second complex components into the Stokes space, thereby yielding a set of Stokes parameters; determine a rotation of the first and second polarization axes based on the set of Stokes parameters; and determine XPOLM compensated first and second complex components by transforming the first and second complex components in accordance to the determined rotation of the first and second polarization axes