This person designs the fibre network before it's built.
Think:

• Where fibre runs
• Splitter locations
• GPON architecture
• Capacity planning
• Greenfield estates
• Apartment buildings (MDUs)
• Transit network connectivity

They're producing designs, drawings and build packs.
Backgrounds 
 

• FTTP Design
• GPON Design
• Fibre Access Network
• HLD/LLD
• Fibre Planning
• Greenfield Design
• MDU Design
• Nokia ISAM
• GIS
• AutoCAD
• SpatialNet
• Comsof