CWDM (Coarse Wavelength Division Multiplexer) is a sparse wavelength division multiplexer, also known as a coarse wavelength division multiplexer. DWDM (Dense Wavelength Division Multiplexer) is a dense wavelength division multiplexer.
CWDM and DWDM have different channel spacing. Channel spacing refers to the difference between the nominal carrier frequencies of two adjacent channels and can be used to prevent interference between channels.
The wavelength interval between CWDM channels is 20 nm, while the channel interval of DWDM is 1.6 / 0.8 / 0.4 nm (200 GHz / 100 GHz / 50 GHz), which is much smaller than CWDM.
The difference in channel spacing also causes the difference in bandwidth and capacity that CWDM and DWDM can carry. DWDM modules can further increase system bandwidth and capacity by using closely spaced wavelengths to carry more signals on the same fiber.
The biggest advantage of the CWDM system is the low cost. The cost of the device is mainly reflected in the filter and laser. The wide wavelength interval of 20nm also brings the advantages of low technical requirements for the laser and simplified structure of the optical multiplexer / demultiplexer for CWDM. The structure is simplified and the yield is improved, so the cost is reduced. The increase in the cost of DWDM is mainly due to the high cost of laser diodes and the cooling laser technology used to maintain wavelength stability.
