Thank you for the file. As you mentioned, it is not necessary to use loop to get to the fiber length you want to get like this. You can put only the fiber link in the loop to avoid calculation repetition for all the other components. I changed the loop number to 1 and the fiber length to 500m (as in the paper) and you can have the results at the receiver. Please do this and let me if your problem is solved.
Regards