Performance evaluation of multilevel polarisation shift keying modulation schemes

The performance of coherent optical transmission systems using multilevel polarisation modulation is derived in terms of the symbol error probability. Four new multilevel modulation schemes based on equipower signal constellations at the vertices of regular polyhedra inscribed into the Poincare sphere are proposed. For an increasing number of signals in the constellation, the shot noise performance of these systems show a remarkably less rapid degradation with respect to standard multilevel schemes with an equal number of signals.