Performance Analysis of RSA Encrypted Secure Free-Space Optical Communication Link Under Adverse Atmospheric Conditions Implemented on a Testbed

The increasing interest in the field of free-space optical communication (FSOC) can be attributed to the rising demand for an alternate communication system that can replace the existing communication systems. FSOC ranges from a few meters of indoor communication to a few kilometers of terrestrial range to satellite communication. The challenges posed vary in different scenarios. For indoors, major challenges are the artificial light sources, and for outdoors, it is the atmospheric channel-related concerns, such as fog, smoke, wind flow, and the turbulence of the channel. These adverse atmospheric conditions will degrade the link performance. On the other hand, the demand for secure communication links from the physical layer to the network layer is ever-increasing. In this paper, we have conducted a simulation study for various modulation techniques in different atmospheric conditions and have demonstrated the integration of a Rivest–Shamir–Adleman (RSA) encrypted link that offers security along with various digital modulation schemes. We have designed a lab-level setup for FSOC and developed various testbeds to simulate adverse atmospheric conditions. We tested FSOC link performance by measuring the bit error rate with various modulation schemes, that is, OOK (NRZ, RZ), PPM, and DPIM formats, along with RSA on the testbed. Received: 28 April 2025 | Revised: 24 June 2025 | Accepted: 2 September 2025 Conflicts of Interest The authors declare that they have no conflicts of interest to this work. Data Availability Statement Data are available from the corresponding author upon reasonable request. Author Contribution Statement Dhanush Devappa B C: Conceptualization, Methodology, Software, Formal analysis, Investigation, Data curation, Writing – original draft, Writing – review & editing, Visualization. Chandani Kashyap: Validation, Investigation, Data curation. Shreyas Jain: Validation, Formal analysis, Data curation, Writing – review & editing. Soumit Banerjee: Methodology. Appala Venkata Ramana Murthy: Conceptualization, Resources, Data curation, Writing – original draft, Writing – review & editing, Visualization, Supervision, Project administration.