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 . These are the outdoor fiber optic cables you see strung along telephone poles (aerial), installed inside an underground duct, or even buried directly below ground. 2 meters (3-4 feet) deep to reduce the likelihood of accidentally being dug up. It affects performance, maintenance, cost, and reliability.