In the dynamic landscape of telecommunications, optical networks have become the backbone of high-speed data transmission systems, reshaping global information flow. To optimize and share this pervasive infrastructure, there's a call for the introduction of disaggregation and openness in optical networking. Openness enables the possibility to implement an optical network digital twin (DT), which is the core for an optimized software-defined management of a complex system. The virtualization and SDN, achieved thanks to the DT development, allow the exploitation of Network-as-a-Service paradigm (NaaS). The adoption of NaaS offers several advantages, enabling a more agile and cost-effective network deployment, allowing organizations to scale their infrastructure based on demand.