HOM visibility under pulsed operation. (a) Visibility and v-factor as a function of the laser repetition rate. The delay is actually obtained varying the laser repetition rate, which determines the temporal overlap between the photon wave packets. (b) Coincidences histogram for 125 ns-long (25 m) delay line and parallel polarization. (c) Optimal HOM visibility and v-factor vs delay line length; for longest delay (125 ns), also the visibility of the interference between photons separated by multiple fluorescence cycles is reported as colored dots. (d) Coincidences histogram for 15 ns-long delay line and parallel polarization, in the case of 40 MHz repetition rate (interference between photons separated by five fluorescence cycles).