Laser linewidth is the important determinant of applying coherent optical orthogonal frequency division multiplexing (CO-OFDM) in optical transmission systems. The laser linewidth impairments in 100-Gb/s polarization division multiplexing CO-OFDM (PDM-CO-OFDM) system without optical dispersion compensation are compensated by the phase drift compensator (PDC) based onMth-power-law method located at the receiver. PDC is more effective to compensate the phase drift due to laser linewidth. Simulating results show that the maximum Q factor can be increased by almost >10.0 dB for back-to-back (BtoB). For the 100-kHz linewidth system of 800-km system, a benefit of about 4.9 dB is possible for the maximum Q factor.