Polarization mode dispersion measurements on single-mode optical fiber

As field applications for optical fiber are extended to longer distances, higher digital data rates, and analog applications for video transport, the need for tighter distortion limits is increasing. While designing systems to operate closer to the zero dispersion wavelength will help to minimize the impact of chromatic dispersion, a secondary dispersion effect, polarization mode dispersion, becomes the next limiting factor. Polarization mode dispersion arises from the fact that, even in today´s fibers which have excellent geometry and low internal stress, a small level of birefringence exists. This birefringence causes temporal distortion of the signal due to slightly different propagation velocities of the two orthogonal polarizations which constitute the “single-mode”