OPTICAL FIBER CABLES AND RACEWAYS

A. General 770-1. Scope. The provisions of this article apply to the installation of optical fiber cables and raceways. This article does not cover the construction of optical fiber cables and raceways. 770-2. Locations and Other Articles. Circuits and equipment shall comply with (a) and (b) below. (a) Spread of Fire or Products of Combustion. See Section 300-21. (b) Ducts, Plenums, and Other Air-Handling Spaces. Section 300-22, where installed in ducts or plenums or other space used for environmental air. Exception to (b): As permitted in Section 770-53(a). 770-3. Optical Fiber Cables. Optical fiber cables transmit light for control, signaling, and communications through an optical fiber. 770-4. Types. Optical fiber cables can be grouped into three types. (a) Nonconductive. These cables contain no metallic members and no other electrically conductive materials. (b) Conductive. These cables contain noncurrent-carrying conductive members such as metallic strength members and metallic vapor barriers. (c) Composite. These cables contain optical fibers and current-carrying electrical conductors, and shall be permitted to contain noncurrentcarrying conductive members such as metallic strength members and metallic vapor barriers. Composite optical fiber cables shall be classified as electrical cables in accordance with the type of electrical conductors. 770-5. Optical Fiber Raceway System. A raceway system designed for enclosing and routing only nonconductive optical fiber cables. Where optical fiber cables are installed in a raceway, the raceway shall be of a type permitted in Chapter 3 and installed in accordance with Chapter 3. ARTICLE 770 - OPTICAL FIBER CABLES AND RACEWAYS 70-783 Exception: Listed optical fiber raceway. (FPN): Plastic innerduct commonly used for underground or outside plant construction may not have appropriate fire safety characteristics for use as an optical fiber optic cable wiring method within buildings. 770-6. Cable Trays. Optical fiber cables of the types listed in Table 770-50 shall be permitted to be installed in cable trays. (FPN): It is not the intent to require that these optical fiber cables be listed specifically for use in cable trays. 770-7. Access to Electrical Equipment Behind Panels Designed to Allow Access. Access to equipment shall not be denied by an accumulation of wires and cables that prevents removal of panels, including suspended ceiling panels. B. Protection 770-33. Grounding of Entrance Cables. Where exposed to contact with electric light or power conductors, the noncurrent-carrying metallic members of optical fiber cables entering buildings shall be grounded as close to the point of entrance as practicable or shall be interrupted as close to the point of entrance as practicable by an insulating joint or equivalent device. For purposes of this section, the point of entrance shall be considered to be at the point of emergence through an exterior wall, a concrete floor slab, or from a rigid metal conduit or an intermediate metal conduit grounded in accordance with Article 250. C. Cables Within Buildings 770-49. Fire Resistance of Optical Fiber Cables. Optical fiber cables installed as wiring within buildings shall be listed as being resistant to the spread of fire in accordance with Sections 770-50 and 770-51. 770-50. Listing, Marking, and Installation of Optical Fiber Cables. Optical fiber cables in a building shall be listed as being suitable for the purpose, and cables shall be marked in accordance with Table 770-50. Exception No. 1: Optical fiber cables shall not be required to be listed and marked where the length of cable within the building does not exceed 50 feet (15.2 m) and the cable enters the building from the outside and is terminated in an enclosure. (FPN): Splice cases or terminal boxes, both metallic and plastic types, are typically used as enclosures for splicing or terminating optical fiber cables. Exception No. 2: Conductive optical fiber cable shall not be required to be listed and marked where the cable enters the building from the outside and is run in rigid metal conduit or intermediate metal conduit and such conduits are grounded to an electrode in accordance with Section 800-40(b). Exception No. 3: Nonconductive optical fiber cables shall not be required to be listed and marked where the cable enters the building from the outside and is run in raceway installed in compliance with Chapter 3. 70-784 NATIONAL ELECTRICAL CODE Table 770-50. Cable Markings Cable Marking Type Reference OFNP Nonconductive optical Sections 770-51(a) fiber plenum cable and 770-53(a) OFCP Conductive optical Sections 770-51(a) fiber plenum cable and 770-53(a) OFNR Nonconductive optical Sections 770-51(b) fiber riser cable and 770-53(b) OFCR Conductive optical Sections 770-51(b) fiber riser cable and 770-53(b) OFNG Nonconductive optical Sections 770-51(c) fiber general-purpose cable and 770-53(c) OFCG Conductive optical Sections 770-51(c) fiber general-purpose cable and 770-53(c) OFN Nonconductive optical Sections 770-51(d) fiber general-purpose cable and 770-53(c) OFC Conductive optical Sections 770-51(d) fiber general-purpose cable and 770-53(c) (FPN No. 1): Cable types are listed in descending order of fire resistance rating. Within each fire resistance rating, nonconductive cable is listed first, since it may substitute for the conductive cable. (FPN No. 2): See the referenced sections for requirements and permitted uses. 770-51. Listing Requirements for Optical Fiber Cables and Raceways. Optical fiber cables shall be listed in accordance with (a) through (d) below, and optical fiber raceways shall be listed in accordance with (e) and (f) below. (a) Types OFNP and OFCP. Types OFNP and OFCP nonconductive and conductive optical fiber plenum cables shall be listed as being suitable for use in ducts, plenums, and other space used for environmental air and shall also be listed as having adequate fire-resistant and low-smokeproducing characteristics. (FPN): One method of defining low-smoke-producing cables is by establishing an acceptable value of the smoke produced when tested in accordance with the Test I for Fire and Smoke Characteristics of Wires and Cables, NFPA 262-1990 (ANSI) to a maximum peak optical density of 0.5 and a maximum average optical density of 0.15. Similarly, one method of defining fire-resistant cables is by defining maximum allowable flame travel distance of 5 feet (1.52 m) when tested in accordance with the same test. (b) Types OFNR and OFCR. Types OFNR and OFCR nonconductive and conductive optical fiber riser cables shall be listed as being suitable for use in a vertical run in a shaft or from floor to floor and shall also be listed as having fire-resistant characteristics capable of preventing the carrying of fire from floor to floor. (FPN): One method of defining fire-resistant characteristics capable of preventing the carrying of fire from floor to floor is that the cables pass the requirements of the Standard Test for Flame Propagation Height of Electrical and Öptical-Fiber Cable Installed Vertically in Shafts, ANSI/UL 1666-1986. ARTICLE 770 - OPTICAL FIBER CABLES AND RACEWAYS 70-785 (c) Types OFNG and OFCG. Types OFNG and OFCG nonconductive and conductive general-purpose optical fiber cables shall be listed as being suitable for general-purpose use, with the exception of risers and plenums, and shall also be listed as being resistant to the spread of fire. (FPN): One method of defining resistance to the spread of fire is for the damage (char length) not to exceed 4 feet 11 inches (1.5 m) when performing the "Vertical Flame Test - Cables in Cable Trays," as described in Test Methods for Electrical Wires and Cables, CSA C22.2 No. 0.3-M 1985. (d) Types OFN and OFC. Types OFN and OFC nonconductive and conductive optical fiber cables shall be listed as being suitable for generalpurpose use, with the exception of risers, plenums, and other space used for environmental air, and shall also be listed as being resistant to the spread of fire. (FPN): One method of defining resistant to the spread of fire is that the cables do not spread fire to the top of the tray in the "Vertical-Tray Flame Test" in the Reference Standard for Electrical Wires, Cables and Flexible Cords, ANSI/UL 1581-1985. Another method of defining resistant to the spread of fire is for the damage (char length) not to exceed 4 feet 11 inches (1.5 m) when performing the "Vertical Flame Test - Cables in Cable Trays," as described in Test Methods for Electrical Wires and Cables, CSA C22.2 No. 0.3-M 1985. (e) Plenum Optical Fiber Raceway. Plenum optical fiber raceways shall be listed as having adequate fire-resistant and low-smoke-producing characteristics. (f) Riser Optical Fiber Raceway. Riser optical fiber raceways shall be listed as having fire-resistant characteristics capable of preventing the carrying of fire from floor to floor. 770-52. Installation of Optical Fibers and Electrical Conductors. (a) With Conductors for Electric Light, Power, or Class 1 Circuits. Optical fibers shall be permitted within the same composite cable for electric light, power, or Class 1 circuits operating at 600 volts or less only where the functions of the optical fibers and the electrical conductors are associated. Nonconductive optical fiber cables shall be permitted to occupy the same cable tray or raceway with conductors for electric light, power, or Class 1 circuits operating at 600 volts or less. Conductive optical fiber cables shall not be permitted to occupy the same cable tray or raceway with conductors for electric light, power, or Class 1 circuits. Composite optical fiber cables containing only current-carrying conductors for electric light, power, or Class 1 circuits rated 600 volts or less shall be permitted to occupy the same cabinet, cable tray, outlet box, panel, raceway, or other termination enclosure with conductors for electric light, power, or Class 1 circuits operating at 600 volts or less. Nonconductive optical fiber cables shall not be permitted to occupy the same cabinet, outlet box, panel, or similar enclosure housing the electrical terminations of an electric light, power, or Class 1 circuit. Exception No. 1: Occupancy of the same cabinet, outlet box, panel, or similar enclosure shall be permitted where nonconductive optical fiber cable is functionally associated with the electric light, power, or Class 1 circuit. 70-786 NATIONAL ELECTRICAL CODE Exception No. 2: Occupancy of the same cabinet, outlet box, panel, or similar enclosure shall be permitted where nonconductive optical fiber cables are installed in factory- or field-assembled control centers. Exception No. 3: In industrial establishments only, where conditions of maintenance and supervision assure that only qualified persons will service the installation, nonconductive optical fiber cables shall be permitted with circuits exceeding 600 volts. Exception No. 4: In industrial establishments only, where conditions of maintenance and supervision assure that only qualified persons will service the installation, hybrid optical fiber cables shall be permitted to contain current-carrying conductors operating over 600 volts. Installations in raceway shall comply with Section 300-17. (b) With Other Conductors. Optical fibers shall be permitted in the same cable, and conductive and nonconductive optical fiber cables shall be permitted in the same cable tray, enclosure, or raceway with conductors of any of the following: (1) Class 2 and Class 3 remote-control, signaling, and power-limited circuits in compliance with Article 725. (2) Power-limited fire protective signaling systems in compliance with