Experiment on Coherent Optical RZ 8-Star QAM Systems Using Decision-Aided Maximum Likelihood Phase Estimation

In this letter, a return-to-zero 8-star quadrature amplitude modulation (QAM) signal is generated for the first time by using a parallel I/Q modulator followed by an amplitude modulator with binary drive signals. Our experimental results verify the theoretically derived approximate bit-error rate and ring ratio optimization algorithm of the 8-star QAM. Decision-aided maximum likelihood phase estimation (PE) shows comparable performance with V&V
$M$
th-power PE, but with much less computational complexity.