Patent ID: 7082229

Claim:
An apparatus for compensating or emulating polarization mode dispersion (PMD) effects occurring in an optical signal traveling over an optical fiber based link, comprising: birefringence sections, controllable polarization transformation devices, each birefringence section including birefringence optical members or parts thereof, each birefringence section being followed or preceded by one of the controllable polarization transformation devices, the birefringence sections being at least three in number, at least one of the birefringence sections having a propagation delay time different from that of the other birefringence sections, and two of the birefringence sections having propagation delay times of around T c and αT c respectively, and the remaining birefringence sections having a total propagation delay time of around (1−α) T c with T c such that DGD _ 4 ≤ T c ≤ 2 ⁢ ⁢ DGD _ where {overscore (DGD)} is an average differential group propagation time of the PMD to be compensated or emulated and with 0<α<1.