Fig. 6: Results for assessing the crosstalk in the dual-channel 16QAM.

a, b The measured constellation diagrams in the two groups of experiments, where the received and reference symbols are represented by the blue square and red circular markers, respectively. a The diagrams in the first group of experiments where sixteen different symbols are sent to user 1 and the same symbols coded as “0000” to user 2. b The diagrams in the second group of experiments where sixteen different symbols are sent to user 2 and the same symbols coded as “0011” to user 1. c The cross-talk values of dual users.