Hello Gagan ,the time you mentioned above is too long.As far as Dwdm system is concerned then the total transmitted power is high than a single channel.The major reason for the long calculation time is your power Secondly you are using HNLF which is realized by increasing non linear index gamma .Now small power even can take more time in hnlf due to very small affective area of fiber and due to gamma .Moreover if you used Smf and dcf in your system then it will take very much time.The cause you need address is your power and could you please tell how many channels you fed to HNLF? Attach system file for better help And there is some reduction in calculation time if you use latest version.