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Experimental demonstration of encryption system using two-dimensional pattern for secure free-space optical communication

A secure free-space optical (FSO) communication system that physically introduces a two-dimensional pattern as a key is proposed for further improving the possibility of FSO communication. This paper presents the results of basic experiments conducted with the proposed encryption system for FSO communication that confirm the encryption and restoration of binary data streams in the proposed system configuration. Further, we define a pattern selection measure to improve the quality of the decoded signal in the encryption method by using a spatial pattern, and also evaluate the decoded signal obtained from the experimental results.