This study presents the haze and the rainfall effect on FSO link system in tropical rainforest region. These two natural phenomena caused high signal attenuation as they create limited distance for visibility. This condition contributes to the impairment of the FSO link performance. With the analysis through theoretical, simulation and measurement the haze and rainfall effect can be investigated. Various transmission wavelength of FSO system is applied to investigate the attenuation effect on the system. The finding analysis shows that the low visibilities contribute high attenuation to transmission links. This attenuation effect can be reduced by manipulating several parameters such as narrow beam divergence, small transmitter and larger area receiver, longer wavelength medium and APD detector. As a result, the maximum visibility can be predicted that can begin impair the link. Overall, wavelength 785 nm improves the free space optic system by 14% compared to other wavelengths. Thus the continuous good link transmission can be acquired.
