Comprehensive study of orbital angular momentum shift keying systems with a CNN-based image identifier

Different possible configurations of orbital angular momentum shift keying (OAM-SK) systems with an image identifier based on convolutional neural network (CNN) are comprehensively studied in this paper. These configurations transmit information by employing different OAM modes (eigenmodes, conjugate modes or multimodes) at the transmitter side and utilize coherent or incoherent detection at the receiver side. We analyze firstly the OAM mode property, the property of free-space channel with atmospheric turbulence (AT), the CNN-based image identifier, and then discuss the feasibility and performance of all possible OAM-SK configurations. We quantitatively study and compare the available OAM-SK configurations with different AT strength and transmission distances in terms of demodulation accuracy. Results show that the coherent systems outperform their incoherent counterparts in terms of the demodulation accuracy. In addition, the OAM-SK configuration with eigenmode and coherent detection has the highest demodulation accuracy among all the possible configurations.