Laser communication based on a multi-channel single-photon detector

We demonstrate a free-space laser communication system with a multi-channel single-photon detector to improve the efficiency of transmission. On account of the photon-number-resolving capability, the discrimination level is adjustable to optimize the extraction of effective signals from the background noise. This method greatly reduces the error bit rate even under the high intensity of the background noise of 6×106 counts/s in daylight. Meanwhile, combined with the pulse position modulation, the bandwidth of the laser communication system can be improved greatly. This study paves the way to the high accuracy and high speed free-space optical communication for 24 h a day.