For testing QKD hardware in-field, PTB offers two fiber connections: 1. The “Niedersachsen Quantum Link“ (https://doi.org/10.1016/j.measen.2024.101774): This testbed consists of a 78 km long pair of dark fibers (losses approx. 24 dB) between the cities of Hannover and Braunschweig and is operated by the Physikalisch-Technische Bundesanstalt and the Leibniz Universität Hannover. One of the dark fibers is reserved for “quantum” applications, while the second fiber is dedicated to the dissemination of time and frequency reference signals as well as classical communication between two sites. This combination of dark “quantum” fiber and integrated time-frequency infrastructure is a unique feature of the Niedersachsen Quantum Link testbed. 2. Intracity link: a second duplex fiber connection is available connecting PTB to a node within the city of Braunschweig. This connections allows for one-way (14 km, 7 dB) and looped tests (28 km, 14 dB).