Performance of Encoding, Encryption, and Modulation Schemes in Free-Space Optical Communication Evaluated on the Atmospheric Testbed

Abstract

In this paper, we investigate the adverse atmospheric effects, including wind disturbance, dry fog, wet fog, and smoke conditions, which are simulated on an atmospheric testbed specifically built for free-space optical communication (FSOC) experiments. We have also developed an FSOC system that can modulate the optical signals with the choice of the modulation, encoding scheme, and encryption. A robust, secure link that is operated by the user from a single graphical user interface. We have further tested the secure link with two encryption schemes, three error correction codes, and five different modulation formats with various combinations and in different atmospheric conditions. We have evaluated the link performance by two important metrics, that is, execution time and bit error rates. The results obtained can explicitly show the effect of the adverse channel. Initial experiments, with a clean chamber, showed the behavior of link performance with data rate. Further results show that the smoke chamber can adversely impact the FSOC system with an early onset of error occurrence and contributes to 10–20% of additional error compared to a clean chamber. Among error correction codes, the Reed–Solomon code helps to improve the error in all adverse conditions. This study further expands to the real-time and on-field investigation of free-space optical links for better performance.

Received: 27 October 2025 | Revised: 29 January 2026 | Accepted: 7 May 2026

Conflicts of Interest

The authors declare that they have no conflicts of interest to this work.

Data Availability Statement

Data sharing is not applicable to this article as no new data were created or analyzed in this study.

Author Contribution Statement

Shashank Shekhar: Conceptualization, Methodology, Validation, Formal analysis, Investigation, Writing – original draft, Writing – review & editing, Visualization. Dhanush Devappa B C: Methodology, Software, Data curation, Writing – original draft. Moksh Chandrakar: Investigation. Appala Venkata Ramana Murthy: Resources, Writing – original draft, Supervision, Project administration, Funding acquisition.