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 . Using Conduits to Protect Underground Fiber Cables In areas exposed to moisture, mechanical stress, or future excavation, installing fiber optic cable within an underground conduit provides an additional layer of protection. 2 meters (3-4 feet) deep to reduce the likelihood of accidentally being dug up. As a leading manufacturer of end-to-end fiber optic solutions, Weunion specializes in engineering.