The Network Functions Manager - Transport (NFM-T) is Nokia's management platform for its optical transport network portfolio, including the 1830 PSS family. Its fundamental purpose is to provide the full lifecycle management of the optical network. This includes the initial design and planning assistance, configuration and service provisioning, and ongoing monitoring and assurance. Therefore, the statement that NFM-T is used to design and manage the optical network is the most accurate and comprehensive description of its role among the given options.

A. The term "fully supports... L2 applications" is an overstatement. While NFM-T provisions L2 services over optical gear, comprehensive L2/L3 VPN service management is the domain of the NFM-P.

B. NFM-T is the domain controller for optical transport nodes. IP/MPLS nodes are managed by a different domain controller, the Network Functions Manager – Packet (NFM-P).

D. This describes a primary use case but is not a complete definition of NFM-T's role. NFM-T provisions optical services between various endpoint types, not exclusively IP nodes.

1. Nokia Network Services Platform (NSP) Optical Network Management and Control Solution Sheet: This document explicitly states that the solution enables operators to "simplify and automate the end-to-end process of designing, provisioning and troubleshooting optical services". This directly supports the "design and manage" scope described in the correct answer. (Reference: Nokia Solution Sheet, "NSP Optical Network Management and Control", 2021).

2. Nokia Network Services Platform (NSP) Data Sheet: This data sheet describes the NSP architecture, clearly delineating the roles of the domain controllers. It specifies the "NSP Network Functions Manager–Transport (NFM-T)" for managing the optical domain and the "NSP Network Functions Manager–Packet (NFM-P)" for the IP/MPLS and Ethernet domain. This confirms the separation of functions, invalidating option B and clarifying the scope limitation in option A. (Reference: Nokia Data Sheet, "Network Services Platform (NSP)", Document ID: SR2104021113EN, April 2021, Page 3).

3. Nokia Application Note, "IP-optical coordination with the Nokia Network Services Platform": This document details the use case of provisioning optical paths for IP routers. It states, "The NSP automates the creation of optical transport services that are optimized to meet the needs of IP/MPLS router-to-router connectivity." While this shows that option D describes a valid and important function, it presents it as a specific application of the broader management capabilities, not the sole or defining purpose. (Reference: Nokia Application Note, Document ID: SR1701004121EN, January 2017, Page 2).