Multiple InGaAs/InP single-photon avalanche detector scheme for wavelength-division-multiplexed quantum communications in a single transmission fiber

We propose a wavelength-division-multiplexed (WDM) scheme for high-speed and high-capacity quantum communications in a single transmission fiber. The scheme involves multiple weak coherent-state signal pulse sources (WCS-SPSs) and multiple single photon detectors (SPDs). Quantum signals encoded with WDM WCS-SPSs are transmitted through a standard single mode fiber to a receiver composed of WDM SPDs. This WDM scheme can provide high transmission capacity by avoiding the afterpulse effect of InGaAs/InP single-photon avalanche detectors (SPADs) but by adding up the total avalanche counts. We performed numerical calculations on the reduced afterpulse effect and the increased total quantum transmission capacity of the WDM scheme based on measured avalanche count data and previously reported afterpulse data from the InGaAs/InP SPADs. The results indicate that the WDM scheme provides increased quantum transmission capacity by avoiding increased afterpulse effects despite increased insertion loss and crosstalk due to the WDM devices.