Comparison of two modulation formats at spectral efficiency of 5 bits/dual-pol symbol

Two modulation formats at spectral efficiency of 5 bits/dual-pol symbol are compared. Linewidth tolerances and feed-forward carrier recovery methods are discussed. Performances over uncompensated SMF and LEAF fibers are shown. The 4-D optimized format is found to be modestly better than a hybrid combination better th of PM-QPSK and PM-8QAM.