Performance analysis of physical-layer security in mid-infrared FSO communication system

Based on the eavesdropping model of non-line-of-sight (NLOS) scattering channel in mid-infrared (MIR) free-space optical (FSO) communication system, the physical-layer security is analyzed theoretically by considering the effects of the atmospheric turbulence, atmospheric attenuation, and beam divergence attenuation. The effects of atmospheric turbulence, transmission distance, and visibility on secrecy capacity and interception probability are investigated. Secrecy capacity and interception probability of near-infrared (NIR) system are compared with those of MIR system. It is theoretically demonstrated that the secrecy capacity of the NIR system is smaller than that of the MIR system. Closed-form expression of interception probability is derived. Furthermore, in the same visibility condition, the interception probability of the MIR system is much lower than that of the NIR system. Therefore, compared with the NIR system, MIR system has much better performance of physical-layer security.