We present a 625 MHz clocked coherent one-way quantum key distribution (QKD) system which continuously distributes secret keys over an optical fibre link. To support high secret key rates, we implemented a fast hardware key distillation engine which allows for key distillation rates up to 4 Mbps in real time. The system employs wavelength multiplexing in order to run over only a single optical fibre and is compactly integrated in 19-inch 2U racks. We optimized the system considering a security analysis that respects finite-key-size effects, authentication costs, and system errors. Using fast gated InGaAs single photon detectors, we reliably distribute secret keys with rates up to 140 kbps and over 25 km of optical fibre, for a security parameter of 4E-9.
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