Grounding tail cables are required for fiber optic cables with metallic components to ensure safety and compliance with NEC and industry standards.

When Grounding is Required

Fiber optic cables themselves transmit data as light and are non-conductive, so the fiber core does not require grounding. However, cables with metallic components—such as steel armor, copper strength members, aluminum moisture barriers, or metallic messenger wires—must be grounded to prevent electric shock, equipment damage, and fire hazards . Fully dielectric cables with no metal content do not require grounding . Grounding is particularly necessary when the cable enters a building or terminates outside a building and is exposed to contact with power conductors, as specified in NEC Article 770.93 and 770.100 .

Grounding Tail Cable Installation

1. Identify Metallic Components: Determine if the fiber optic cable contains metallic elements that can conduct stray current .
2. Select Grounding Conductor: NEC allows a minimum of 14 AWG copper, but manufacturers often recommend a 6 AWG copper strand for both bonding and grounding purposes .
3. Bonding Point: Connect the grounding tail cable to the building's grounding electrode system, such as the Telecommunications Main Grounding Busbar (TMGB) or Central Office Ground Busbar (COG Busbar) .
4. Conduit and Pathway Considerations: Metallic conduits or trays carrying fiber optic cables must also be grounded, independent of the cable itself .
5. Length and Routing: The grounding conductor should be as short as practicable (generally less than 20 feet) and run in as straight a line as possible to maintain continuity .

Best Practices

• Use insulating joints or equivalent devices to interrupt metallic members if grounding is not feasible or required by code .
• For armored fiber cables, bonding and grounding are mandatory, whereas dielectric-armored cables can provide protection without grounding .
• Always consult local authority having jurisdiction (AHJ) for compliance with local codes, as they may differ from NEC or ANSI/TIA standards .

Summary

A fiber optic grounding tail cable is essential for conductive fiber optic cables to safely bond metallic components to the building's grounding system. Proper identification of metallic elements, correct conductor sizing, and adherence to NEC and industry standards ensure both safety and network reliability .