Measurement of single-photon detection efficiency of InGaAs/InP avalanche photodiodes in wavelength-division-multiplexed schemes

We report on experimentally measured detection efficiency of single-photon detectors (SPDs) based on wavelength-division-multiplexed (WDM) InGaAs/InP avalanche photodiodes (APDs). Multiple SPDs combined in a WDM scheme can be used to overcome the detection speed limit of a single SPD. There is a tradeoff between the detection efficiency of parallel SPDs in the WDM scheme and the optical loss caused by the WDM devices.