21.4 Optical Fiber Cables & Communications Systems Entering Buildings (2026 Articles 720–723, 800, 810, 820)

What changed in 2026

The 2026 NEC removed the independence of Chapter 8 and consolidated limited-energy wiring:

• Articles 770 (Optical Fiber Cables) and 805 (Communications Circuits) were deleted. Their inside-the-building requirements moved into Articles 720 (general wiring methods), 722 (cables, including listing, marking, and substitutions), and 723 (raceways, cable routing assemblies, and cable trays).
• Article 800 now covers communications systems outside and entering buildings: entrance cables, primary protection, and bonding at the entrance.
• Article 742 covers overvoltage protection and Article 750 covers grounding and bonding for limited-energy systems.
• Articles 810 (radio and television equipment), 820 (community antenna television and radio distribution), 830 (network-powered broadband), and 840 (premises-powered broadband) continue for their specific systems.

Optical fiber cable types

Cable substitutions

A cable with a higher fire rating may replace a lower one in the same space: plenum cable may be used where riser or general-purpose cable is required, and riser cable where general-purpose cable is required. Nonconductive cable may substitute for conductive cable of the same or lower rating (for example, OFNP for OFCP or OFCR), but conductive cable may not substitute for nonconductive cable. Plenum spaces need plenum-rated cable or cable in a raceway suitable for the plenum.

Optical fiber with electrical conductors

Installation inside buildings (Articles 720 to 723)

• Cables must be supported by the building structure, not by ceiling grids or ceiling-support wires, and installed so they do not block access to equipment above suspended ceilings.
• Penetrations of fire-resistant-rated walls, floors, and ceilings must be firestopped.
• Abandoned optical fiber and communications cables: the accessible portion must be removed, unless tagged for future use.
• Cables in plenums must be plenum rated; cables in vertical risers between floors must be riser rated or in a raceway or fireproof shaft as permitted.
• Raceways and cable routing assemblies used for these cables must have the same fire rating as the space (plenum, riser, or general purpose).

Communications entering buildings (Article 800)

Entrance cables

• Unlisted outside plant cable: unlisted communications or optical fiber cable may be installed in building spaces other than risers and plenums where the length within the building, measured from the point of entrance, does not exceed 50 ft, and the cable terminates in an enclosure or on a listed primary protector. The point of entrance may be extended by enclosing the entrance cable in RMC or IMC to the point of emergence.
• Conductive members: the metallic members of conductive optical fiber cable and the metallic sheath of communications cable entering a building must be bonded or grounded as close as practicable to the point of entrance.

Primary protectors and bonding

• A listed primary protector is required on each communications circuit that is exposed to lightning or accidental contact with power conductors, located as close as practicable to the point of entrance.
• Bonding conductor: copper or other corrosion-resistant conductive material, insulated, at least 14 AWG, with a current-carrying capacity at least equal to the outer sheath or protected conductors, run as straight as practicable, and protected where exposed to physical damage.
• Connection point: to the building's intersystem bonding termination (250.94), or to the grounding electrode system, the power service equipment enclosure, the grounding electrode conductor, or another permitted point.
• Length at one- and two-family dwellings: the bonding conductor or grounding electrode conductor must be as short as practicable and not longer than 20 ft. If 20 ft cannot be achieved, a separate electrode (such as a ground rod) may be installed for the protector and bonded to the power grounding electrode system with at least 6 AWG copper.

Antennas and CATV

• Radio and television antennas (Article 810): masts and metal structures supporting antennas, and the antenna discharge unit, must be bonded to the building's grounding means with a copper bonding conductor of at least 10 AWG for receiving stations; outdoor antennas and lead-ins must be kept away from power conductors and may not be attached to poles carrying power circuits over 250 V.
• CATV (Article 820): the outer conductive shield of coaxial cable entering a building must be bonded as close as practicable to the point of entrance, with the same 14 AWG minimum and 20 ft dwelling limit for the bonding conductor; unlisted outside coaxial cable may extend no more than 50 ft inside.

Worked example: fiber in a commercial building

A contractor brings a single-mode fiber cable with a steel armor (conductive, OFC-type outside plant cable) into a building and runs it to a telecom room 120 ft away.

1. Entrance: the unlisted outside plant cable may extend only 50 ft inside unless enclosed in RMC or IMC from the point of entrance; at the 50 ft limit, splice it in an enclosure to a listed indoor cable.
2. Bonding: bond the steel armor as close as practicable to the point of entrance, to the intersystem bonding termination.
3. Indoor cable: the route passes through a return-air plenum, so the indoor cable must be OFNP or OFCP, or be in a plenum-rated raceway.
4. Shared raceway: if it must share a raceway with 277 V lighting conductors, only a nonconductive (OFN-type) cable is permitted.