Recommended technical requirements are detailed by reference to IEC 60794-3-11 on outdoor optical fibre cables for duct, directly buried, and lashed aerial applications. The following formulas may be used to determine general guidelines for installing Corning Optical Communications fiber optic cable; however, refer to the cable specifi simply double the minimum working bend radius. Split cable guides and split 40-in. There are many requirements for laying direct-buried optical cables, and the direct-buried depth of optical cables is one of them. Panduit does not guarantee any favorable results or assume any liability in connection with this document. Note that Recommendation ITU-T L.