  We propose a characterization method for the overall detection efficiency,
afterpulse and dark count probabilities of single-photon counting modules in
real-time with simple instrumentation. This method can be applied when the
module is running in its intended application, and is based on monitoring the
statistics of the times between consecutive detections. A mathematical model is
derived and fit to the data statistical distribution to simultaneously extract
the characterization parameters. The feasibility of our scheme is demonstrated
by performing measurements on three commercial devices based on cooled InGaAs
APD operating in gated mode. Different statistical ensemble lengths were
analyzed and results assess the scheme for real-time application.
