Parallel Coded Optical Vortex Beam Free-Space Communication Based on Single-Photon Detection

A free-space communication scheme is proposed based on orbital angular momentum (OAM) states and pulse position modulation (PPM). It can not only improve the channel capacity, but also be suitable for single-photon detection to realize in case of ultra-weak light. parallel coding method high-capacity low bit error rate (BER) under high background. Theoretical simulation experimental results show that effectively suppress background noise. The BER as 1.27 × 10 $^{-5}$ condition 16 OAM states, detectors (SPDs) coincidence, noise notation="LaTeX">$^{7}$ counts per second. performance an order magnitude better than traditional PPM, capacity increased by 12 times. This work provides effective solution deep space high-speed communication.