18 wavelengths from 1270 to 1610, GB-Link MUX join any numbers of any wavelength together at the transmitter, and the Demux at the receiver to split them apart, extra upgrade(express)/1310 supervisory/tap monitor port can be added to the Mux/Demux based on customer needs. WDM Mux/Demux are popular with telecommunications companies because they allow them to expand the capacity of the network without laying more fiber.