As I wrote I have tested it successfully in trunk mode without the fibre cable between.
Can it be that the media converter don`t forward trunk? (When this sounds now completely crazy I am sorry I don`t have a clue about fibre)
I have also tested two new gigabit media converter from d-Link but they cannot at least connect to each other. Can it be that the fibre cable is crap? With the old media converter 100FastEthernet I got at least a "access"-connectivity.