The single pulse detection and false-alarm probability in measuring time of flight (TOF) of laser pulse are caused by the creation of primary electrons in Geiger mode avalanche photodiode (APD). Measuring the detection and false-alarm probabilities with longer laser pulse than time bin and artificial noise source, we have experimentally proved that the creations of primary electrons in Geiger mode APD is Poisson distributed. It is also shown theoretically that there is little difference between smaller and larger laser pulse width than time bin cases on measurements of both detection and false-alarm probability. (C) 2009 Elsevier B.V. All rights reserved.