What is Fiber Optic Cable Jacket & Fire Rating

Updated on Sep 27, 2021 by

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An optical fiber jacket is the outer protective layer of an optical fiber cable. It safeguards the fibers from abrasion, moisture, chemicals, and other external elements that could compromise their integrity and performance, ensuring optical fiber cable's longevity, performance, and reliability in various applications. This article introduces the fiber optic jackets, and explains their materials and fire ratings.

Why Fiber Optic Jacket is Important?

As the following figure shows, the fiber optic jacket is the outermost protective layer of a fiber cable, and then the strength member, coating, and fiber core in sequence. As the first defense line, the optical fiber jacket not only offers protection but also aids in identification. For example, OS2 fibers typically have yellow optical jackets, while OM4 fibers are usually aqua. Regardless of the color, these optical fiber jackets are made from specialized materials to safeguard the fiber cables.

fiber optic cable

What are The Materials of Fiber Optic Jackets？

Fiber optic cable jacket materials are diverse, including polyvinyl chloride (PVC), low smoke and non-halogen (LSZH), polyethylene (PE), etc., and these materials have different fire resistance properties. When selecting fiber optic cables, the specific installation environment and safety requirements should be considered to select the appropriate jacket material to ensure transmission efficiency and system safety. The following table provides an overview of the main characteristics and application scenarios of the four common fiber optic cable jacket materials:

Jacket Material	Benefit of Jacket Material
PE (Polyethylene)	PE has excellent properties of moisture and weather resistance, and has the good electrical properties over a wide temperature range. It's also abrasion resistant. So PE is the standard jacket material for outdoor fiber optic cables.
PVC (Polyvinyl Chloride )	PVC is usually low-cost, flexible, fairly rugged, and a flame/oil-resistant material, so it can be formulated to function in a variety of environments and applications. In other words, it can be used as the jacket materials for both indoor and outdoor cables.
PVDF (Polyvinyl Difluoride)	PVDF is used for plenum cables, because it has better fire-retardant properties than PE and produces little smoke.
LSZH (Low Smoke Zero Halogen)	LSZH jacket is free of halogenated materials which can be transformed into toxic and corrosive matte during combustion. LSZH materials are used to make a special cable called LSZH cable, which is a good choice for inner installations. But it is the most expensive jacket material.

What are fiber optic jacket rating？

Typically, there are eight levels of fire resistance for both non-conductive and conductive cables specified by NEC (National Electrical Code). All indoor fiber optic cables must be marked and installed properly for its intended use: plenums, risers and general purpose areas.

NEC Code	Description	Cable Application	Possible Substitute
OFNP	Optical Fiber Non-conductive Plenum Cable	Plenum, overhead, fiber only	/
OFCP	Optical Fiber Conductive Plenum Cable	Plenum, overhead, hybrid (fiber/wire)	/
OFNR	Optical Fiber Nonconductive Rise Cable	Riser, backbone, fiber only	OFNP
OFCR	Optical Fiber Conductive Rise Cable	Riser, backbone, hybrid	OFCP
OFNG	Optical Fiber Nonconductive General-Purpose	General purpose, horizontal	OFNP, OFNR
OFCG	Optical Fiber Conductive General-Purpose	General purpose	/
OFN	Optical Fiber Nonconductive	General purpose, horizontal, fiber only	OFNP, OFNR
OFC	Optical Fiber Conductive	General purpose, horizontal, hybrid	OFCP, OFCR

FAQs about FS Color Coding Cabling System

Q: OFNP vs. OFNR, what are the differences?

A: As mentioned above, OFNP and OFNR are two types of fiber optic cables that are used in buildings. OFNP cables have fire-resistance and low smoke production characteristics. This is the highest fire rating fiber cable and no other cable types can be used as substitutes. So these cables are mostly installed in plenum areas. Whereas, the fiber-resistance and low smoke of OFNR cables are not good as OFNP. OFNP plenum cables can be used as substitutes for OFNR cables. Through OFNR vs. OFNP, it is worth noticing that OFNR fiber optic cable cannot be used in plenum areas to replace OFNP cables, however, the latter can be used in the riser areas. Both OFNP and OFNR can be used in general purpose areas.

plenum vs riser

Q: What distinguishes plenum, riser, and general purpose areas in a building?

(1) A Plenum area is a building space used for air flow or air distribution system (drop ceiling and raised floors).

(2) A Riser area is a floor opening, shaft or duct that runs vertically through one or more floors.

(3) A general purpose area is all other area that is not plenum or riser and on the same floor.

Q: How to Select the Fiber Optic Cable Outer Jacket Materials Based on the Layout Area?

(1) For Plenum Areas, choose plenum-rated jackets labeled 'OFNP' or 'OFCP'. These are designed to limit smoke and flame spread in air-handling spaces.

(2) In Riser Areas, use riser-rated jackets marked as 'OFNR' or 'OFCR'. These jackets are made to prevent flames from moving between floors through riser spaces.

(3) For General Purpose Areas, general-use cables labeled 'OFNG' or 'OFCG' are sufficient. They are not specifically designed for high fire resistance.

Q: How do the fire ratings of fiber optic cables affect their color code and identification?

A: According to EIA/TIA-598, the fiber optic cable color code defines the jacket color codes for different fiber types (SMF or MMF). For single mode fiber, the jacket color is typically yellow. While for multimode cable, the jacket color can be orange (OM1 & OM2 cable), aqua (OM3 cable) and purple (OM4 cable). For outside plant cables, the standard jacket color is black.