Single photon detectors based on avalanche photodiodes (SPADs) are essential in applications that require high resolution, such as quantum communications and quantum metrology. The effect of the width of photon detection gate is little explored, and there are no studies for the wavelength range of interest in telecommunications around 1550 nm. In this work, a proposal is presented for analyzing the impact of the detection gate width of an InGaAs/InP SPAD, performing a statistical analysis of consecutive detections and the probability detection of 0 or 1 events depending on the optical attenuation. The average number of photons per gate measured by the SPAD was varied, and the results were evaluated for the values of 4 ns, 8 ns, 12 ns, 16 ns and 20 ns of detection gate widths, and Expanded Measurement Uncertainty was estimated for each test. The results obtained indicate an adequate optical power range for calibrating a SPAD with a detection efficiency of 15 percent and dead – time of 1 microssecond, in the range of 10 nW to 0,15 nW. In this power range, the respective products, which are associated with an effective average number of photons per gate window, correspond to the values of 190 x 10(-4) to 0,32 x 10(-4) (for 4 ns) e 140 x 10(-4) to 2,9 x 10(-4) (for 8 ns). Linear behaviors were obtained for the adjustment of the calibration curves for gate widths of 4 ns and 8 ns.