Hi Saruchi Attri,
I am looking into your design file to find some solution. But I want to mention one thing that for the FSO channel you are taking an attenuation of 0.11 dB/km which is far lesser that fiber i.e. 0.2 dB/km whereas it is 20 dB/km. So please change that value to respective default one though it is for simulation you can take but that system will not be practical one. i will let you know If I get a solution to your issue. Thanking you.
Regards,
Dhiman