In this paper, we present a comprehensive survey of attenuation due to rain conditions in the months of monsoon in Delhi region. In this paper I used Marshal and Palmer rain distribution model for four specific months of the rainfall i.e. June to September for calculate simulation model for rain attenuation. I analyzed Q-factor of the received signal by varying the transmission wavelength, data rate and range of the FSO system. The simulation results show that for error free transmission of data during the months of rainfall, the transmission signal wavelength in the longer wavelength region at a wavelength of 1300nm and 1550nm is recommended to be used for a maximum data rate of 2.5Gb/s with a maximum transmission range up to 4Km. Delhi being a highly populated (with the IT hub) city the demand for higher and unlimited bandwidth for communication channel is highly required. For this case the communication through FSO is the best alternative solution than optical fiber.
