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). The Fiber Optic Association, Inc. (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. Split cable guides and split 40-in. 1. The methods described are intended for guideline use only, as it is impossible to cover all the various conditions that may arise during an installation. During installation, all curvatures should be smooth.