Multiplexers are also known as MUX or passive Mux. The technology integrates multiple communication channels over one physical medium. On one side the communication channels are “muxed” together to then go over the dark fiber. At the other end this is reversed in the process of “demuxing” the channels. The communication signals can have speeds from 1G, 10G, 40G, and 100G. There are two different techniques used for multiplexing which have different grids or channel spacing: The first one is CWDM, or Course Wavelength Division Multiplexing, which ranges from 1270nm to 1610nm with 20nm steps. The maximum channels a CWDM can have is 18. Solid Optics stocks the 8 channel and the 18 channel. The other technique is DWDM where the 'D' stands for Dense. This typically has a spacing of 0.8nm and is around 1550nm. The max channels you can use is 80, but many of our customers use the 8, 16, and 40 channel.
Both techniques have advantages and disadvantages. We are designing dark fiber networks every day and can advise you which technique will best fit your project requirements.