  The detection sensitivity (DS) of the commercial single-photon-receiver based
on InGaAs gate-mode avalanche photodiode is estimated. Instalment of a
digital-blanking-system (DBS) to reduce dark current makes the difference
between DS, which is an efficiency of the detector during its open-gate/active
state, and the total/overall detection efficiency (DE). By numerical
simulations, it is found that the average number of light-pulses, blanked by
DBS, following a registered pulse is 0.333. DS is estimated at 0.216, which can
be used for estimating DE for an arbitrary photon arriving rate and a gating
frequency of the receiver.
