# Fuzzy Logic-Based Performance Enhancement of FSO Systems Under Adverse Weather Conditions
## 3 Fuzzy Modeling for Enhancing Receiver Performance in FSO System
### Adaptive BER Threshold Adjustment Mechanism for FSO-FLC-OCDMA Receivers
Results indicate a consistent trend showing that the received optical power decreases as both the FSO link distance and rainfall rate increase. For instance, under LR, the received optical power at a distance of 2.8 km is \(-14.9\) dBm. Maintaining a similar value of the received power level, the FSO range is reduced to 2.07 km when the rainfall rate is changed to MR. Finally, in the case of HR, the received optical power at an FSO link of 1.2 km is \(-13.8\) dBm. Figure 10 depicts the Q-factor performance across various transmission distances for LR, MR, and HR scenarios. The analysis reveals that rainfall-induced attenuation surpasses that of haze, leading to a decline in system performance and reducing the transmission distance. Figure 10: Q-factor vs. FSO range under rainy weather. Figure 9: Received power vs. FSO range under rainy weather. Under LR, as shown in Figure 11, the system achieves a distance of 2.8 km with a log(BER) of \(-6.3\), which is less compared to the distance observed under LH conditions. Maintaining the same log(BER) value, the FSO transmission distance decreases to 2.07 km under MR conditions. For HR, the signal propagates to a distance of 1.2 km. Figure 12 presents the eye diagrams for channel 1 of the proposed FSO system employing SSM codes, evaluated at transmission distances of 2.8 km (LR), 2.07 km (MR), and 1.2 km (HR). The distinct and well-defined eye openings observed at these distances provide clear evidence of successful data reception under varying rain conditions. Figure 11: log(BER) vs. FSO range under rainy weather. Figure 12: Eye diagrams under (**a**) LR at 2.8 km, (**b**) MR at 2.07 km, and (**c**) HR at 1.2 km. #### 4.1.2 Foggy Weather

Foggy weather conditions present a more significant challenge to FSO transmission compared to hazy or rainy conditions due to higher attenuation levels. Consequently, the proposed system exhibits a reduced FSO transmission distance in foggy environments, as evidenced in Figures 13-15. These figures illustrate the relationship between received optical power, Q-factor, and log(BER) with transmission distance in different fog conditions. Numerical values show that the longest FSO span of 2.1 km is achieved under LF conditions with a received optical power of approximately \(-14\) dBm. As the fog intensity transitions to MF, this distance reduces to 1.4 km. Under HF conditions, an achievable distance is 1.1 km. This is because LF causes less signal attenuation than HF. The Q-factor at 2.1 km under LF conditions is 6. For MF, the Q-factor is 5.6 at 1.4 km. Maintaining the same Q-factor observed under MF conditions, the FSO range decreases to 1.1 km under HF conditions, which is shown in Figure 14. The log(BER) values at 2.1 km (LF), 1.4 km (MF), and 1.1 km (HF) are \(-9.2\), \(-8\), and \(-8\), respectively. These values highlight the significant impact of fog on the performance of the proposed FSO system. With an increase in the fog density, the system transmission distance and signal quality are significantly affected, as shown in Figure 7:0

Finally, Figure 16 displays the eye diagrams for channel 1 of the proposed FSO system utilizing SSM codes at transmission distances of 2.1 km (LF), 1.4 km (MF), and 1.1 km (HF). The wider eye openings across these distances serve as compelling evidence of successful data reception under varying fog conditions. Figure 7:1 Q-factor vs. FSO range under foggy weather. Figure 7:2 Received power vs. FSO range under foggy weather. ### Performance Evaluation of FSO-SSM System with FLC Under Rain and Fog

The performance of the proposed FLC mechanism is evaluated by comparing BER outcomes with and without FLC under different weather impairments. Both graphical

Figure 7:3 Eye diagrams under (**a**) LF at 2.1 km, (**b**) MF at 1.4 km, and (**c**) HF at 1.1 km. Figure 7:4 log(BER) vs. FSO range under foggy weather. results and a quantitative summary table are provided to validate the adaptive behavior of the FLC.