Please upload your files.
It is working well with me.
if you have a problem with DSP matlab component and has Optisys13. go to Receivers Library then go Digital signal processing.
Attach DSP for QPSk for your design in the place of the DSP matlab component.get the dispersion values from SM fiber and add it to the DSP for QPSK component.
It gives the same results or better.
Let me know your progress.