Dear all,

I am trying to couple the output of a RC telescope into a single mode fiber. The fiber used is from Corning with mode field diameter 10 micrometers at 1550 nm. In this system, I am facing some main problems. 

1. The coupling efficiency as given by the fiber coupling option in the analysis tab and the coupling efficiency as given by the operand FICL is different. So, when I optimize the system to increase the coupling efficiency using the FICL operand, the coupling efficiency as given by the fiber coupling option is found to decrease. I have done both the analysis by neglecting the source fiber and only the receiver fiber is considered.
2. Second concern is regarding which criterion to choose while tolerancing the system. My ultimate aim in both the cases is to have an increased fiber coupling efficiency
3. When I change the length of the fiber, the coupling efficiency is found to decrease. But as per my understanding the coupling efficiency should not be effected by the fiber length.

Any help or suggestions related to this topic would be highly appreciated. The zemax file of the same is attached below.

Thanking you in advance

Rakhi