What is CWDM System?

- Mar 16, 2021-

CWDM is a low-cost WDM transmission technology for the access layer of the metropolitan area network. In principle, CWDM uses an optical multiplexer to multiplex optical signals of different wavelengths into a single optical fiber for transmission. At the receiving end of the link, the mixed signal in the optical fiber is decomposed into different wavelengths by means of an optical demultiplexer. Signal, connect to the corresponding receiving device.

Due to the wide wavelength interval of the CWDM system, the requirements for the technical indicators of the laser are relatively low. Since the wavelength interval reaches 20nm, the maximum wavelength shift of the system can reach -6.5℃~+6.5℃, the laser emission wavelength accuracy can be relaxed to ±3nm, and in the working temperature range (-5℃~70℃), the temperature The wavelength drift caused by the change is still within the allowable range, and the laser does not need a temperature control mechanism, so the structure of the laser is greatly simplified and the yield is improved.

In addition, the larger wavelength interval means that the structure of the optical multiplexer/demultiplexer is greatly simplified. For example, the number of coating layers of the filter of the CWDM system can be reduced to about 50 layers, while the number of coating layers of the 100GHz filter in the DWDM system is about 150 layers, which leads to higher yields, lower costs, and greatly increases the number of filter suppliers. Conducive to competition. The cost of CWDM filter is more than 50% less than that of DWDM filter, and it will be further reduced with the increase of automated production technology and batch size.

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