Comprehensive and Detailed Explanation From Nokia Optical Networking Fundamentals:
While technologies like WSS (Wavelength Selective Switches) and coherent transmission (100G/200G/400G+) significantly improve the efficiency and reach of a network, the most direct way to increase the total transportable volume of services in a mesh topology is to upgrade link capacity or install new physical links. In Nokia optical planning, upgrading link capacity typically involves moving from a lower-rate system (like 10G) to a higher-rate system (like 100G or 400G) or increasing the number of available wavelengths by expanding from a 40-channel to an 80-channel or 96-channel C-band system.
Adding new links (new fiber spans) creates more degrees in the mesh, providing more paths for traffic and increasing the overall aggregate bandwidth of the network. Option A refers to flexibility (ROADM functionality) rather than raw capacity. Option B (PRC) relates to survivability and availability, not capacity expansion. While Option C (coherent transmission) is a powerful method for increasing capacity per wavelength, it is not the "only" way, as adding more fiber (spatial multiplexing) or more channels (spectral density) are also primary methods for scaling a mesh network to handle more services.

The validate step in the EPT design process is used to trigger the run design action, which is responsible for verifying the consistency of the network design and fixing any errors that may exist. During the validation process, the system will compare the configuration available on the involved network elements and the design provided by EPT, and any discrepancies will be flagged for further investigation or correction.

Yes, the user can apply manual changes but only for non-GMPLS nodes, as the control plane reserves node resources not editable by the user. The edit EPT menu allows the user to view information about a node but is not used to modify node parameters. The user can only apply manual changes to non-GMPLS nodes, as the control plane reserves node resources which cannot be modified by the user.

It is possible to open and manage EPT designs that are created with different releases than the release installed on the local workstation, however only designs created with current and older releases can be opened and edited. Designs created with an older release can be opened by a current release but changes cannot be made.

The Metro Area Network (MAN) is a telecommunications network that spans a metropolitan area and connects multiple local area networks (LANs) or business networks together. It typically covers an area that is larger than a LAN but smaller than a wide area network (WAN). The purpose of a MAN is to provide a high-bandwidth, low-latency communication infrastructure for businesses and other organizations in a metropolitan area.
Reference:
Cisco, "Metro Ethernet Services," https://www.cisco.com/c/en/us/solutions/service-provider/metro-ethernet-services/index.html Techopedia, "Metro Area Network (MAN)," https://www.techopedia.com/definition/26896/metro-area-network-man