WDM equipment is divided into passive WDM series and semi-active WDM series. It can effectively save fiber resources and network cost, solve the problems of fiber scarcity, multi-service transparent transmission and shorten the construction period, realize the rapid expansion of fiber, can greatly improve the efficiency of fiber core resources of optical cable, minimize the efficiency of the use of tube holes, use optical multiplexer to multiplex optical signals of different wavelengths to a single fiber for transmission, and at the receiving end of the link, with the help of optical demultiplexer, the optical fiber in the At the receiving end of the link, the mixed signals are decomposed into different wavelengths with the help of an optical demultiplexer and connected to the corresponding receiving equipment. In layman's terms, this means that different services are carried on different wavelengths without interfering with each other, thus increasing the fiber transmission capacity.