Bottom-Up Design of Digital Twins for Optical Transport Networks: Challenges and Lessons Learned [Invited]

We discuss the design and development of a digital twin for optical transport networks, focusing on a bottom-up approach aligned with network operators' specific needs. Our methodology was carved by prioritizing operator requirements, aiming to enhance the management and analysis of optical networks. Having a digital twin enabled gathering telemetry data from the network to assess its health and support preventive maintenance. We navigate through various challenges, from model accuracy to user interface design, and share the lessons learned from these experiences, which helped to implement and validate it in real networks.