A polarization mode dispersion generator for generating polarization mode dispersion
("PMD") spectra is provided. The generator includes a plurality of birefringent
stages, each stage including a differential group delay ("DGD") element and a phase-shifting
element. The generator is capable of inducing an amount of polarization mode-mixing
between at least one adjacent pair of stages. The shape of a PMD spectrum can be
preserved while frequency shifting the spectrum in either direction. Alternatively,
the shape of the PMD spectrum can be changed without frequency shifting.
