Atmospheric Turbulence Effect on Acquisition Time of Ground to Satellite Optical Communication System

The performance of ground to deep space optical communication system is degraded by distortion of the beam as it propagates through the turbulent atmosphere. Turbulence causes intensity fluctuations of the received signal which ultimately affect the acquisition time required to acquire and locate the space borne target using narrow laser beam. In this paper, performance of FSO system in atmospheric turbulence has been analyzed in terms of acquisition time for noncoherent and coherent modulation schemes. Numerical results presented in graphical and tabular forms show that the acquisition time increases with the increases in the turbulence level. This is true for both coherent and non coherent modulation schemes. The BPSK has lowest acquisition time among all schemes. In noncoherent modulation schemes, M-PPM performs better than the other schemes. With the increase in M, acquisition time becomes lower, but at the cost of increase in system complexity.