Free-space quantum key distribution transmitter system using WDM filter for channel integration

Autor: Minchul Kim, Kyongchun Lim, Joong-Seon Choe, Byung-Seok Choi, Kap-Joong Kim, Ju Hee Baek, Chun Ju Youn
Jazyk: angličtina
Rok vydání: 2024
Předmět:
Zdroj: ETRI Journal, Vol 46, Iss 5, Pp 806-816 (2024)
Druh dokumentu: article
ISSN: 1225-6463
2233-7326
DOI: 10.4218/etrij.2024-0142
Popis: In this study, we report a transmitter system for free-space quantum key distri-bution (QKD) using the BB84 protocol, which does not require an internal alignment process, by using a wavelength-division multiplexing (WDM) filter and polarization-encoding module. With a custom-made WDM filter, the sig-nals required for QKD can be integrated by simply connecting fibers, thus avoiding the laborious internal alignment required for free-space QKD systems using conventional bulk-optic setups. The WDM filter is designed to multiplex the single-mode signals from 785-nm quantum and 1550-nm synchronization channels for spatial-mode matching while maintaining the polarization rela-tions. The measured insertion loss and isolation are 1.8 dB and 32.6 dB for 785 nm and 0.7 dB and 28.3 dB for 1550 nm, respectively. We also evaluate the QKD performance of the proposed system. The sifted key rate and quantum bit error rate are 1.6 Mbps and 0.62%, respectively, at an operating speed of 100 MHz, rendering our system comparable to conventional systems using bulk-optic devices for channel integration.
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