Low-density parity-check (LDPC) codes combined with polarization scramblers are used to mitigate polarization mode dispersion (PMD) in 40-Gb/s optical fiber system. The simulations are performed to compare the correction performance of LDPC codes and Reed–Solomon (RS) code used in this PMD mitigation scheme. Results show that LDPC codes can achieve a better performance than the RS code with the same redundancy. The scrambling speed of polarization scramblers for LDPC codes system is also discussed, and the optimal speed of 10 MHz is obtained.