Figure 2
From: Field trial of a three-state quantum key distribution scheme in the Florence metropolitan area
Experimental setup. The transmission channel is a dark fiber link connecting LENS laboratory, where Alice and Bob are located, to a telecom datacenter, where a standard optical mirror is installed at the end of the fiber. Laser Q: continuous wave laser at 1560.61 nm; Laser C: continuous wave laser at 1536.61 nm; IM: intensity modulator; PM: phase modulator; BS: beam splitter; VOA: variable optical attenuator; DWDM: dense wavelength division multiplexing filter; DLI: delay-line interferemoter; SPAD: single-photon avalanche detector; APD: avalanche photodiode. In the green square we reported the three quantum states prepared by Alice and propagated through the channel