Similar to CWDM’s mentioned in questions 3 and 4 DWDM’s are used to increase the amount of information or systems that can be transmitted over a single fiber. The DWDM’s will allow for many more channels using much tighter channel spacing. Typical DWDM’s will allow for but not limited to 32, 40 and 44 channels, while the 50GHz spacing will double that and allow for 64, 80 and 88 channels.