Ultralow Photon Flux OWC Links Using UV‐C Single‐Photon Detection

Abstract Low photon flux optical wireless communication (OWC) links are difficult to operate under normal daylight conditions as the interference from daylight will overwhelm any signal. However, in the UV‐C region of the spectrum, light from the sun is highly attenuated, offering the possibility of link operation. In this paper, ultralow photon flux OWC links using a UV‐C micro‐LED and a silicon photomultiplier (SiPM) based UV‐C single‐photon detector (SPD) are reported. A 1 megabaud per second (MB s −1 ) symbol rate 128‐pulse‐position modulation (128‐PPM) link is demonstrated with 7.7 transmitted photons per bit, corresponding to 0.97 detected photon per bit. A maximum bit rate of 120 Mbit s −1 is achieved in 8‐PPM links with a transmitted power of 1.7 nW. In addition, a 500 MHz single‐photon link is established with a bit error rate (BER) of and a measured bit rate of 2.12 Mbit s −1 , showing the potential for a quantum key distribution (QKD) system operating at the UV‐C region.