Good morning, I'll try and clarify. There are 5 main components to fiber management in ArcGIS. The utility network, communications utility foundation solution template (data model), ArcGIS apps and APIs, and partner solutions. Esri users doing fiber management in ArcGIS today are leveraging one or more of those components. The utility network itself is a topology or connectivity model that resides in the GDB and in order to use it you need an asset package data model, like the one found in the communications utility network foundation, which provides the data schema and network rules for different types of networks, like fiber. Once you have the utility network and data model in place, you can then start editing features and connecting up the network. This can be done through ArcGIS Pro, other ArcGIS apps, or using the APIs.
So regarding splicing, ArcGIS Pro offers a tool to create connections or associations between features, ie. associating a fiber strand to a port. This tools is used for any type of network, so its very generalized and not built specific for managing a fiber network. So can you connect up a fiber network in core ArcGIS? Yes, but connecting a fiber network specifically is very cumbersome and time consuming because the tools is not built with fiber engineers in mind who have to connect or slice hundreds of strands at a time. So if you are looking for a more user friendly experience ,or a traditional splicing tool, we'd recommend one of our dozen business partners who build these productivity tools for engineers either built on the utility network or built on the other ArcGIS components I mentioned previously.
In the story map below, there are some videos and one of the videos 'modifying network connectivity' highlights how to connect up features in the utility network in core ArcGIS Pro. You'll also find a story map which highlights business partners with fiber solutions.
https://storymaps.arcgis.com/stories/19fd6813361a4ff585b528f77843f88c
Solutions Engineer | Spatial Ninja | GIS ️ | Telecommunications