A ROADM (Reconfigurable Optical Add-Drop Multiplexer) site is a key component in flexible optical networks. It allows the flexible adding and dropping of wavelengths within the site (A), enhancing network agility. It supports automatic optical power adjustment (B), which helps maintain signal quality across the network by balancing power levels and avoiding distortion. Also, when optical-layer ASON (Automatically Switched Optical Network) is required, ROADMs must be used (C) to provide dynamic wavelength routing and switching capabilities. However, ROADMs are not mandatory for electrical-layer ASON, so (D) is false.
These features collectively enable efficient, dynamic optical networking with minimal manual intervention, critical in advanced transmission scenarios covered by HCIP-Transmission.