Dear Anamika and Sam Sung,
I just want to clarify my point first. You are right, Anamika, it is preferable to use the existing fiber optical links due to reasons of economical efficiency. When I was answering your question about the differences between DWDM and CWDM, I meant the large effective area fibers would be more efficient from design point of view. The difference DWDM and CWDM for existing fiber optical links is the trade-off between the capacity (higher in DWDM) and “reach” (higher in CWDM).