Hi Sasha,
I checked it by comparing it to the OptiSystem sample coherent 4-QAM and I must say I got really different constellations by the changes I applied to the implementations. By changing M-ary pulse generators bias and gain (gain=-2, bias=2) which were the main problem I think, I managed to get the constellation you can see. It was the best I could achieve although I tried make changes exactly according to the QAM sample. Here I have used coherent receiver component, even though yours was all right.
Regards
