In Wavelength Division Multiplexing (WDM), an open eye diagram indicates that the signal quality is good. An open eye suggests that the signal has low noise and is less susceptible to distortion, inter-symbol interference, and jitter.
Channels in FlexGrid systems are not allocated with a granularity of 27.5 GHz. FlexGrid systems typically have a granularity of 12.5 GHz, making option B the false statement.
A pre-amplifier in an optical network is used to amplify the optical signal at the receiver side after it has traveled through the fiber from another node. This helps in improving the signal quality and ensures it is strong enough to be correctly processed by the receiving equipment.