Coarse Wavelength Division Multiplexer (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.       

      CWDM equipment is small in size and easy to maintain. The laser of the CWDM system does not require

semiconductor coolers and temperature control functions, which can significantly reduce power consumption and

provide convenient power supply. It can use 220V AC power, and the equipment cost is low, which can reduce the

operating cost of the network.  

      A typical CWDM wavelength division multiplexing system can provide 8 optical channels, and up to 18 optical

channels according to the ITU-T G.694.2 specification. CWDM equipment has no special requirements for optical

fibers. G.652, G.653, and G.655 optical fibers can be used. Existing optical cables can be used to significantly

increase the transmission capacity of optical fibers and improve the utilization of optical fiber resources. CWDM is

gaining more and more applications in fields such as telecommunications, broadcasting and television, enterprise

networks, and campus networks.