We perform a systematic measurement of the degree-of-polarization (DOP) and eye-closure penalty for optical signals with orthogonal polarizations. We find that the symmetry of DOP is maintained for the orthogonal polarizations under both first and higher order polarization-mode dispersion (PMD), whereas the symmetry of eye-closure penalty is broken under second-order PMD. An orthogonal polarization pair can have large disparity of eye-closure penalty despite an identical DOP. We also demonstrate a novel approach to estimate the maximum eye-closure penalty asymmetry with three orthogonal polarizations on the Poincare sphere.
Shieh, W; Hui, R; Yi, X. Degree-of-polarization and eye-closure penalty associated with optical signals with orthogonal polarizations. IEEE PHOTONICS TECHNOLOGY LETTERS. May 2006. 18(10) : 1122-1124