Arezu Rezazadeh - Department of Electrical Engineering, Ferdowsi University of Mashhad
Ghosheh Abed Hodtani - Department of Electrical Engineering, Ferdowsi University of Mashhad

In this paper, by using a simple mathematical inequality, we derive a $ new upper bound fkr the capacityof$ free space optical channel in coherent case. Then, by applying general fading distribution, we obtainan upper bound for mutual information in non-coherent case. Finally, we derive the correspondingoptimal input distributions for both coherent and non-coherent cases, compare the results with previousworks numerically and illustrate that our results subsume some of previous results in special cases

Mathematical Inequality, Capacity, Upper Bound, Free Space Optical Channel, Optimal Input Distributions