Versatile wavelength-division multiplexed quantum key distribution network operating simultaneously in the O and C bands

Ongoing technological progress is accelerating the commercial and global-scale deployment of Quantum Key Distribution (QKD). Its ability to enable unconditionally secure communication is expected to be a key feature of future telecommunication networks, and practical demonstrations of QKD network implementations in real-world environments are crucial for ensuring reliable adoption. In this work, we demonstrate a four-node photonic QKD network that employs versatile and cost-effective wavelength-division multiplexing across three transmitters in the O- and C-bands to simultaneously distribute quantum-secure keys among all nodes. Specifically, the broadband central receiver node shares all optical and electronic decoding components, except for the single-photon detectors, across the three QKD links, significantly reducing system costs and enhancing compactness.