*4.2.1. Sana'a city*

Low visibility range for Sana'a city in Fig. 21 extends from 0.3 to 6 km. Scattering coefficient at low visibility of 0.3 km is 11.37, 10.99 and 8.69 km-1 for wavelengths of 780, 850 and 1550 nm, respectively. The scattering coefficient of 6 km low visibility is 0.45, 0.41 and 0.21 km-1 for wavelengths of 780, 850, and 1550, respectively.

**Figure 21.** Scattering coefficient (km−1) versus low Visibility for Sana'a city (km).

**Figure 20.** Total attenuation (dB) versus link range (km).

196 Contemporary Issues in Wireless Communications

rainfall rate

link range

*4.2.1. Sana'a city*

**rainfall**

**Table 9.** Results of total attenuation for design parameters at rainy days parameters.

wavelengths of 780, 850, and 1550, respectively.

performance of FSO system in environment of Sana'a, Aden and Taiz cities.

**4.2. Simulation results and discussion of haze effects on FSO in Sana'a, Aden, and Taiz cities** In this section, we study the effect of atmospheric attenuation and scattering coefficient on the

Low visibility range for Sana'a city in Fig. 21 extends from 0.3 to 6 km. Scattering coefficient at low visibility of 0.3 km is 11.37, 10.99 and 8.69 km-1 for wavelengths of 780, 850 and 1550 nm, respectively. The scattering coefficient of 6 km low visibility is 0.45, 0.41 and 0.21 km-1 for

**total attenuation/dB**

light 14.3 14.46 moderate 14.5 14.67 heavy 14.71 14.98

light 15.1 15.5 moderate 15.4 16.8 heavy 15.6 20

**from to**

**Figure 22.** Atmospheric attenuation (dB) versus low visibility (km) for Sana'a City.

Figure 22 shows that the atmospheric attenuation versus low visibility in Sana'a city. At low visibility of 0.3 km, atmospheric attenuation is 49.4 dB, 47.7 dB and 37.7 dB for wavelengths of 780, 850 and 1550 nm, respectively. For 6 km low visibility, the atmospheric attenuation is about 2 dB, 1.8 dB and 0.94 dB for wavelengths of 780, 850 and 1550 nm, respectively.
