Integrated four-channel all-fiber up-conversion single-photon-detector   with adjustable efficiency and dark count
  Up-conversion single photon detector (UCSPD) has been widely used in many research fields including quantum key distribution (QKD), lidar, optical time domain reflectrometry (OTDR) and deep space communication. For the first time in laboratory, we have developed an integrated four-channel all-fiber UCSPD which can work in both free-running and gate modes. This compact module can satisfy different experimental demands with adjustable detection efficiency and dark count. We have characterized the key parameters of the UCSPD system. 
Ming-Yang Zheng, Guo-Liang Shentu, Fei Ma, Fei Zhou, Hai-Ting Zhang,   Yun-Qi Dai, Xiuping Xie, Qiang Zhang and Jian-Wei Pan
physics.ins-det physics.optics quant-ph