Increased dimensionality of SP-MQAM modulation higher than 4D to 8D

In this letter we introduce two eight dimensional set partition mQAM (SP-8D-QAM) modulation formats for coherent optical communication as SP-8D-16QAM and SP-8D-32QAM, focusing on their improved spectral efficiency (SE) of up to 3.75 and 4.75 b/s/Hz/pol respectively. We compared the SP-8D-QAM modulation formats to PM-16QAM, PM-32QAM, 128ary SP-QAM and 512ary SP-QAM, and showed the trade-off between their spectral efficiency and asymptotic power efficiency. To achieve the eight dimensionality, we added time as orthogonal channels to both polarization X and Y, in-phase I and quadrature Q for signals mapping. The simulation results show that both SP-8D-16QAM and SP-8D-32QAM give an intermediate performance compromise between 128ary SP-QAM and PM-16QAM and between 512ary SP-QAM and PM-32QAM respectively.