WDM is a technology to solve the shortage of optical fiber resources. Its main purpose is to increase the available bandwidth of optical fiber without laying more optical fibers. CWDM and DWDM are two WDM technologies widely used in telecom. They are mainly used in Mux/Demux, which must be used with WDM optical modules. In the literal sense these two technologies are just different in the density of wavelength, but their actual technology and applications are very different. The following ""ribes the differences between CWDM and DWDM optical modules.
CWDM carrier channel spacing is wider, at 20nm between each wavelength. Therefore, it supports up to 16 wavelength channels transmitted through a fiber at the same time. DWDM carrier channel spacing is narrower, at only 0.2nm, 0.4nm, 0.8nm, or 1.6nm between each wavelength, supporting up to 160 wavelength channels though a fiber at the same time.
Working wavelength range of CWDM is 1270nm - 1610nm, while that of DWDM is selected from CWDM, including 1525nm - 1565nm (C-band) and 1570nm - 1610nm (L-band).
CWDM modulation laser uses uncooled laser, which is electronically modulated, while DWDM uses cooled laser, which is temperature modulated. Due to the uneven temperature distribution over an optical wavelength range, it is difficult and costly to implement temperature modulation, therefore, the cost of DWDM technology is much higher than that of CWDM.
DWDM optical module can accomplish the transmission of long-distance and large-capacity trunk network. DWDM optical modules and equipment are also applied in some large-capacity metropolitan area network core nodes, telecom 5G, metropolitan area network, backbone network and some data centers. Compared with DWDM, CWDM optical modules are of much lower cost and are mainly used in MAN access layer, enterprise network, campus network and so on. CWDM optical module is widely used, which greatly saves the cost of network upgrade.
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