Fig. 6

Recurrence plots. Each recurrence plots represents a 1000 points long time window(10 ns). The six time windows chosen are the ones that have the maximum and minimum DET values in the six time regions with DET values larger or smaller than the confidence levels respectively. a 14 ns–24 ns, (b)36 ns–46 ns, (c) 57 ns–67 ns, (d) 65 ns–75 ns, (e) 83 ns–93 ns, and (f) 111 ns–121 ns