Hirundo‘s coarse wave divider (CWDM) is the use of optical multiplexer to multiplex the optical signal of different wavelengths to a single fiber for transmission, in the receiving end of the link, with the help of the optical solution multiplexer to break down the mixed signal in the fiber into different wavelengths of signal, connected to the corresponding receiving device. It can save fiber resources and network ingmon costs, and it solves the problems of fiber shortage and multi-service transparent transmission.