Hello Gurvinder singh
By doing the modifications i have said above,you will get ber 0 i.e error free communication over the distance you have taken.you can enhance the total transmission distance by launching more power in to the fiber.But higher values of power rise the non linearities .You can use the NF noise figure 4dB instead 6dB in the optical amplifier.EDFa with less that 6dB NF are available now.