A functioning CV-QKD system is provided in which components (receivers, modulators, lasers, etc) and signal processing blocks (frequency and phase recovery, polarization recovery, etc) can be exchanged for test purposes. The system utilizes single-sideband modulation, locally generated local oscillator and polarization-diverse heterodyne detection. The full physical communication layer is provided by AIT. All optical and electronic components can be exchanged by the device to be tested, provided that they meet some physical limitations (such as working at the correct wavelength, 1550nm, their bandwidths match that of the components they have to connect to, etc). Sub-component alterations are generally not possible (i.e. we can test a balanced receiver, but not a single photodiode), but depending on the exact situation this might be accommodated. See the figure annexed for what are considered "components" in this system.