A system for reducing the influence of polarization mode dispersion (PMD) in high speed fiber optical transmission channels. A signal is forward error correction (FEC) encoded according to an FEC code that defines a specified error tolerance per codeword. The invention then effectively randomizes the input polarization of the signal before transmission, in order to reduce the likelihood that PMD will distort one or more codewords beyond the allowed error tolerance. The invention will thereby increase the PMD-limited transmission distance in an optical transmission system.