Your system is correct and results are very close to the paper .there were no such issue in your system .it works fine ,i have made a mistake in my last system about the use of dual drive mzm .i have used dual drive mzm insead of dual port dual drive.Your eye diagram also very much close to as shown in paper.So now you can work further on the system.
In general i have some doubts regarding the cpfsk freq. And bitspersymbol.in papwr i think they havnt written this regarding such values.from results you got and in paper it is observed that thay have used default cpfsk component with same 50 MHz value and 6 per bit.