Hydrophysics

Hydrophysics

Investigation of Atmospheric Conditions and Transmitter Power Budget Effects on Bit Error Rate, Data Rate, and Signal-to-Noise Ratio in a Free-Space Optical Channel under Fog and SmokeInvestigation of Atmospheric Conditions and Transmitter Power Budget Effects on Bit Error Rate, Data Rate, and Signal-to-Noise Ratio in Free-Space Optical Channels under Fog and Smoke

Document Type : Original Article

Authors
Mahdi Akbari
Saeed Olyaee
Faculty of Electrical Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran.
Abstract
The performance of free-space optical (FSO) communication systems is strongly affected by environmental factors such as atmospheric conditions, humidity, and the presence of fog and smoke along the propagation path. In this study, the performance of pulse position modulation (PPM), non‑return‑to‑zero (NRZ), and return‑to‑zero (RZ) modulation formats is analyzed and compared in terms of signal‑to‑noise ratio (SNR), bit error rate (BER), and achievable data rate under different atmospheric conditions, including fog. The FSO link is simulated in MATLAB using a 1550 nm optical source and the Kim atmospheric attenuation model with various visibility ranges, together with standard analytical relations for free‑space optical transmission. The effects of low, moderate, and high atmospheric attenuation, as well as different transmitter power budgets, on BER, SNR, and data rate are evaluated for all three modulation schemes. The results show that PPM is the most effective modulation format, providing lower BER and higher SNR than NRZ and RZ under all attenuation scenarios and for transmitter powers of 1 mW and 5 mW. In particular, PPM maintains better performance in the presence of dense fog and smoke, indicating its robustness for FSO links in harsh atmospheric conditions. The main contribution of this work is the introduction of a real‑time power allocation scheme with low latency and accuracy close to analytical solutions, which enhances the received data rate and improves overall system performance under varying attenuation levels.
Keywords
Free-space optical communication
atmospheric attenuation
modulation schemes
bit error rate
signal-to-noise ratio
Subjects
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  • Receive Date 04 January 2026
  • Revise Date 22 February 2026
  • Accept Date 05 April 2026