When dealing with OTN (Optical Transport Network), there are two main types of Wavelength Division Multiplexing (WDM) systems: Coarse Wavelength Division Multiplexing (CWDM) and Dense Wavelength Division Multiplexing (DWDM). As two modern WDM technologies, they are both used for increasing the bandwidth of fiber by combining optical signals of different wavelengths on one strand of fiber.
CWDM vs DWDM: Transmission Distance
Since DWDM wavelengths are highly integrated with the fiber during light transmission, DWDM is able to reach a longer distance than CWDM. Unlike the DWDM system, CWDM is unable to travel unlimited distances. The maximum reach of CWDM is about 160 km. While an amplified DWDM system can go much further.
CWDM vs DWDM: Modulation Laser
CWDM system uses the uncooled laser while the DWDM system uses the cooling laser. Cooling laser adopts temperature tuning which ensures better performance, higher safety, and longer lifespan of the DWDM system. But it also consumes more power than the electronic tuning uncooled laser used by a CWDM system.
CWDM vs DWDM: Cost
Because the range of temperature distribution is nonuniform in a very wide wavelength, so the temperature tuning is very difficult to realize, thus using the cooling laser technique increases the cost of the DWDM system. Furthermore, the DWDM devices are typically four or five times more expensive than that of a CWDM system. However, the price of a DWDM transceiver is about 20-25% less than a CWDM transceiver on account of the popularization of DWDM.
WDM vs DWDM: Advantages and Disadvantages
As mentioned above, the primary difference between DWDM and CWDM is the channel spacing (CWDM has almost 100 times wider channel spacing). This makes CWDM a simpler technology, resulting in advantages and disadvantages of the different systems with regard to cost, performance, and so on.