Nokia Certified Network Professional – IP/MPLS Services — Question 37

Which of the following statements about coherent transmission in WDM technology is TRUE?

Answer options

• A. Coherent systems need carrier phase information at the receiver.
• B. Only multi-mode fibers can be used with coherent transmissions.
• C. The channel allocation is flexible, according to the channel size of the signals.
• D. At each receiver, a dispersion compensation unit is often necessary, depending on the fiber length.

Correct answer: A

Explanation

The correct answer is A because coherent systems rely on carrier phase information to accurately demodulate the received signals. Option B is incorrect as coherent transmission can also be used with single-mode fibers. C is not accurate because while channel allocation is flexible, it is not solely dependent on the channel size of the signals, and D is misleading as dispersion compensation units are not always necessary at every receiver.