CompTIA Network+ Question B-94

A technician is tasked with connecting a router to a DWDM. The technician connects the router to the multiplexer and confirms that there is a good signal level. However, the interface on the router will not come up. Which of the following is the MOST likely cause?

A. The wrong wavelength was demuxed from the multiplexer.
B. The SFP in the multiplexer is malfunctioning.
C. There is a dirty connector on the fiber optic cable.
D. The fiber optic cable is bent in the management tray.

Correct Answer: A

A multiplexer (or mux) is a device that selects one of several analog or digital input signals and forwards the selected input into a single line. A demultiplexer (or demux) is a device taking a single input signal and selecting one of many data-output-lines, which is connected to the single input. Since the signal going in is good, the problem must be with the signal output. If the correct wavelength was demultiplexed, the interface will be displayed on the router.