Polarization decorrelation in single-mode fibers with randomly varying
birefringence is studied. We find that decorrelation length is minimi
zed for a given beat length if the average autocorrelation length of t
he birefringence is close to the average beat length. The differential
time delay between the polarization modes is found to depend on the a
utocorrelation length of the birefringence rather than on the decorrel
ation length of the polarization modes.