One or more HDPE, PVC or concrete ducts are installed underground, with handholes or manholes at regular intervals. Fiber cables are then pulled or blown through the ducts. A practical, engineering-focused guide to planning and installing underground fiber optic cables with the right cable structure, trench design and protection level for long-life, low-risk networks. Match trench method with the correct underground fiber structure (GYTS, GYTA53, GYTY53, micro-duct). (FOA) was founded in 1995 to help develop the workforce to build the fiber optic networks to support a rapid expansion in communications and the Internet. It forms a critical backbone for modern communication networks across both urban and rural environments.