What is the difference between CWDM/DWDM wavelength division multiplexing equipment?

At present, the effective method to solve the increasing information transmission bandwidth is to use CWDM wavelength division multiplexing equipment and DWDM wavelength division multiplexing equipment, but they are different in many aspects.

(1) Channel spacing

Channel spacing is defined as the difference between the nominal carrier frequencies of two adjacent optical channels and is generally used to prevent inter-channel interference. CWDM wavelength division multiplexing equipment has a wider spacing than DWDM wavelength division multiplexing equipment, which can transmit 18 wavelengths in a spectral grid from 1271 nm to 1611 nm with a channel spacing of 20 nm. DWDM wavelength division multiplexing equipment can transmit 40, 80 or 160 wavelengths, and the channel spacing can be 0.8 nm.

(2)transmission distance

Since the wavelengths of dense wavelength division multiplexing equipment (DWDM) are highly integrated in the optical fiber transmission process, DWDM wavelength division multiplexing equipment can transmit longer distances than CWDM wavelength division multiplexing equipment. CWDM wavelength division multiplexing equipment cannot achieve unlimited distance transmission at present, and its maximum transmission distance is only 160 kilometers, while the transmission distance of DWDM wavelength division multiplexing equipment is far greater than that of CWDM wavelength division multiplexing equipment.

(3) modulated lasers

The system of CWDM wavelength division multiplexing equipment has lower requirements on the technical indicators of the laser, generally using an uncooled laser; the system of DWDM wavelength division multiplexing equipment needs to use a cooling laser, and the cooling laser adopts a temperature adjustment method to ensure the DWDM system. With better performance, higher safety and longer lifetime, DWDM wavelength division multiplexers consume more energy than CWDM wavelength division multiplexing devices using uncooled lasers.

(4) cost

The temperature distribution of the DWDM wavelength division multiplexing equipment system is not uniform in a wide wavelength range, so when the cooling laser technology is used to adjust the temperature, the use cost of the DWDM wavelength division multiplexing equipment system is increased. In addition, a system of DWDM wavelength division multiplexing equipment is also typically four to five times more expensive than a system of CWDM wavelength division multiplexing equipment. However, with the increasing popularity of dense wavelength division multiplexers (DWDM), the price of DWDM optical modules is nearly 20%-25% lower than that of CWDM optical modules.