Investigating Wavelength Dependency of Terrestrial Free Space Optical Communication Link

Free space optical communication involves fiber-less optical based data transmission using visible and infrared bands of the spectrum. This technology has gained huge popularity in the past decades. In recent past a lot of research has been carried out to improve the FSO link performance which is seriously affected due to atmospheric inconsistencies. This paper investigates the performance of free space optical link for different wavelengths. As the laser beam propagates through atmosphere it undergoes attenuation and this attenuation has been calculated for different wavelengths. Moreover the attenuation and scattering due to haze has been studied for different wavelengths. The wavelengths used for this research work are 10 μm, 1.55 μm and 0.85 μm. Finally bit error rate performance of DPSK modulation has been investigated for above mentioned wavelengths and atmospheric turbulence has been modeled using gamma-gamma model. It has been observed that higher wavelengths show less attenuation and moreover the BER performance of DPSK modulation techniques for higher wavelengths is better than that of lower wavelengths.