BER performance analysis of MWIR and SWIR FSO links utilizing aperture averaging technique considering turbulence and various visibility situations with pointing errors

Abstract The atmospheric turbulence and various weather situations deteriorate the system performance of free space optical (FSO) communication. In this article, the ‘bit error rate’ (BER) performance of the ‘mid wavelength infrared’ (MWIR) and ‘short wavelength infrared’ (SWIR) FSO link has been evaluated utilizing the aperture averaging approach with pointing errors in the presence of turbulence and different visibility scenario like fog, haze, clear weather, etc. The transmitter and receiver are 6 km apart, the modulation method is on off keying (OOK), and several aperture sizes at the receiver side have been taken into consideration for the aperture averaging approaches, such as 100 mm, 150 mm, and 200 mm. Additionally, for analysis of the pointing error of both the wavelengths of the FSO link, different beam divergence angle of the transmitter (laser) has been considered. The BER performance is improved with optimum beam divergence angles. The optimization of the divergence angle is independent of wavelengths and visibility conditions. However, the BER has increased more below the optimized divergence angle compared to a larger angle. The MWIR link performs well in poor visibility conditions like fog, whereas the SWIR link fails for the same link distance in both conditions with and without pointing errors.