Hello Gurleen,i have made a system as mentioned in base paper.But they havent mentioned about the parameters of ddmz and cpfsk.So i have tried to make by my own.I was astonished with the results i got from system.I took certain values by countinously varying system iterations on cpfsk freq. And found best results observed when cpfsk freq. Is half of the data rate.in your case it is 1.25 GHz .But system is correct and works fine i have used exact same components that used in base paper.Only thing is change in cpfsk parameters.Look at file and let me now if it helps and try to compare FWM powers with and without these modulators.