Device and method for testing detection efficiency of communication band single-photon detector

The invention provides a device and method for testing the detection efficiency of a communication band single-photon detector, and the specific testing principle is as follows: a spontaneous parametric radiation process in a non-linear optical medium generates correlated photon pairs at a certain probability, i.e., a high-frequency photon is annihilated and two low-frequency photons are generated at the same time; by utilizing the relevance of the correlated photon pair in the aspects of time, energy (frequency), momentum, polarization and the like, the existence of another photon can be forecasted by detecting one photon. The two paths of single-photon counting signals are measured through coincidence measurement, an obtained coincidence measurement value is a counting signal obtained when the two paths of photons are detected at the same time, and the detection efficiency of the to-be-detected single-photon detector can be obtained through the coincidence measurement value, the trigger detection counting v