Distributed Fast Polarisation Scrambling for PMD Mitigation at 43Gb/s

PMD mitigation by distributed fast polarisation scrambling and forward error correction has been demonstrated for the first time at a bit-rate of 43Gb/s. The availability of 5 fast scramblers allowed to study PMD mitigation in a straight SMF fiber line. Whereas the DPSK-NRZ and RZ modulation format at 43Gb/s itself shows a mean DGD of only ~2.5ps (NRZ)and 3.5ps (RZ), this tolerance could be increased by a factor of 3 with a cascade of 5 scramblers to a record value of 8.6ps and 10.2 ps, resp., with 1dB OSNR penalty corresponding to 37% (44%) of the bit period. This high PMD tolerance was already possible at a moderate scrambling speed of 5MHz where no burst error correction of the FEC is visible. The observation of no significant improvement (13%) when increasing the scrambling speed up to 50MHz indicates that fast scrambling based PMD mitigation works successfully with FEC options exhibiting no strong burst error correction capability.