Yenista Optics proposes multiplexers/demultiplexers mounted in a rack for combining transmission lasers. The units are built on request. The customer can define the number of channels between 8 and 96 channels (multiple of 8), channel spacing between 12.5 and 200GHz. The standard for the MUX/DEMUX is single mode fiber, but a polarization maintaining option is available. This option enables simulation of realistic DWDM spectra thanks to a stable output polarization of all the multiplexed transmission lasers that are simultaneously modulated by Mach-Zehnder structures located at the output of the multiplexer. A tap coupler can also be integrated with the multiplexer for monitoring of the WDM comb.