Patent ID: 7218856

Claim:
A communication system using an optical fiber as a transmission line, comprising: a polarization mode dispersion compensation unit compensating for polarization mode dispersion from which an optical signal suffers when traveling through the optical fiber; a polarization mode dispersion measurement unit feeding back information about a state of the polarization mode dispersion from which the optical signal suffers and which is minimally affected by chromatic dispersion, to the polarization mode dispersion compensation unit; a chromatic dispersion compensation unit compensating for chromatic dispersion from which the optical signal suffers when traveling through the optical fiber; and a chromatic dispersion measurement unit disposed closer to a receiver than the polarization mode dispersion compensation unit, feeding back information about a state of the chromatic dispersion from which the optical signal suffers, to the chromatic dispersion compensation unit, wherein, first, polarization mode dispersion is compensated, second, signal degradation by chromatic dispersion after the polarization mode dispersion is compensated is measured, and lastly, chromatic dispersion is compensated based on the measurement of signal degradation.