Polarization fluctuation in optical fibers based on probability

Polarization fluctuations are measured in submarine and underground cables and in long-haul fibers as long as 270 km. The fluctuations are discussed in terms of probabilities using the Poincaré sphere. When the fluctuations are small, the distribution of the polarization state on the Poincaré sphere closely matches a normal two-dimensional distribution. To compensate automatically for the fluctuations, an endlessly rotatable polarization controller is used.