Tag Archives: OFNP

Understanding Optical Fiber Cable Fire Ratings


As we all know, optical fiber cables shall be listed as suitable for the purpose. Cable usually be marked in accordance with NEC (National Electrical Code) Table 770.19. Most manufacturers put the marking on the optical fiber cable jacket every 2′ to 4′. The code does not tell you what type of cable to use (such as single-mode or multi-mode). In fact, It tells you this cable can be resistant to the spread of fire. This text will introduce the knowledge of optical fiber cable fire ratings and help you choose the right fiber for your applications.

Types of Fire-proof Optical Fiber Cable

There are three kinds of cable jacket fire ratings: plenum, riser and general purpose. Plenum cables are held to the most stringent testing of any of the cables rated by the NEC, rated for both flammability and smoke generation. Riser cables are subjected to flame tests only, and are not held to as high of a standard as Plenum rated cables. General Purpose cables may be used anywhere in commercial buildings other than areas where Riser or Plenum cables are required. Besides, optical fiber cable can be divided into nonconductive and conductive according to NEC. Nonconductive cables contain nothing that can conduct electricity, so will not accidentally energize or be energized even when closely associated with electrical conductors. Conductive cables contain noncurrent-carrying conductive members such as metallic strength members, metallic vapor barriers and metallic armor or sheath. Therefore, according to these three cable jackets and whether the cable is nonconductive or conductive, these fire-proof optical fiber cables can be divided into following several types.

Cable Marking Type
OFNP Nonconductive optical fiber plenum cable
OFCP Conductive optical fiber plenum cable
OFNR Nonconductive optical fiber riser cable
OFCR Conductive optical fiber riser cable
OFNG/OFN Nonconductive optical fiber general-purpose cable
OFCG/OFC Conductive optical fiber general-purpose cable

Optical Fiber Cable Fire Ratings

There are three levels of fire resistance in terms of optical fiber cables. The ratings are hierarchical. For example, from a fire resistance standpoint, a higher rating can be substituted for any lower rating, but not vice versa. Also, nonconductive may be substituted for conductive, but not vice versa. The fire ratings of optical fiber are showed below, from most stringent to least.optical fiber cable fire ratings

Choosing the Right Fiber for Your Application

In terms of different cable fire ratings, there are different kinds of optical fiber cables. So choosing the right one becomes a difficult problem. Usually, for those planning or installing a fiber network, the key point of UL 1651 is to help ensure you select the right fiber for your particular need. These are described in article 770.19 of the NEC, but here are some common measures:

  • For a small, in-building deployment, using a riser – OFNP, OFCP, OFNR, OFCR,OFNG, OFCG, OFN, OFC
  • Within an existing, fabricated duct inside a building – OFNP, OFCP
  • In a plenum space that is used for environmental air inside a public building – OFNP, OFCP
  • Inside a fireproof shaft using a riser within any type of building – OFNP, OFCP, OFNR, OFCR,OFNG, OFCG, OFN, OFC
  • When using a metal raceway for in-building deployments covering multiple floors and rooms/apartments – OFNP, OFCP, OFNR, OFCR,OFNG, OFCG, OFN, OFC
  • For vertical runs between floors within a riser – OFNP, OFCP, OFNR, OFCR
  • Within a riser cable routing assembly inside a building – OFNP, OFCP, OFNR, OFCR
  • For in-building deployments with routing only on 1 floor – OFNP, OFCP, OFNR, OFCR,OFNG, OFCG, OFN, OFC

Related Article: Understanding Fiber Optic Cable Jacket & Fire Rating

OFNP: Optical Fiber Nonconductive Plenum Cable


With the wide use of optical fiber cables, more and more people show their interests in plenum fiber optic cable, which is also called OFNP cable. In order to learn about this cable, first of all the meaning of the word “plenum” will be explained. And then we may introduce what the plenum fiber optic cable is. At last, applications of the OFNP cable will be described.

What does a Plenum Area Mean?

A Plenum area is a building space used for air flow or air distribution system. In most buildings, the area above a drop ceiling or under a raised floor is used as the air return (source of air) for the air conditioning. Those drop ceiling and raised floors are also where fiber cables are often installed. The concern is that during a fire, if there is burning material in a plenum air space, smoke and fumes can travel through air ducts to the whole building. For this reason, there are codes to restrict the types of materials (such as cables) that can be placed in the plenum.


In terms of plenum fiber cables, the plenum refers to a cable jacket. National Electrical Code (NEC) requires indoor fiber optic cables be marked with their fire and smoking ratings. According to NEC, a building’s inside area is divided into three types of sections: plenums, risers and general purpose areas. So there are three types of cable jacket in all: plenum, riser, and general purpose. Among plenum cables are held to the most stringent testing of any of the cables rated by the NEC, rated for both flammability and smoke generation.

What is a Plenum (OFNP) Fiber Cable?

7OFNP stands for Optical Fiber Nonconductive Plenum. OFNP is the designation given by the National Fire Protection Association (NFPA) to interior fiber optic cables which contain no electrically conductive component, and which are certified for use in plenum applications. They are engineered to prevent the spread of fire from floor to floor in a building. It is generally intended for horizontal runs especially within an air handing conduit. This type of cable complies with the Underwriters Laboratories (UL) fire safety test Plenum/910. They can be installed in ducts, plenums and other spaces used for building airflow. This is the highest fire rating fiber cable and can’t be replaced with any other cable type.

Plenum (OFNP) Fiber Cable Solutions

Since plenum cables are routed through air circulation spaces, which contain very few fire barriers, they need to be coated in flame-retardant, low smoke materials. These materials offer good resistance against possible fire, so plenum (OFNP) fiber cables have fire-resistance and low smoke production characteristics. And even if in the event that they do begin to burn, they will not emit large quantities of harmful fumes. For these reasons, these plenum fiber cables provide a low cost option for gigabit Ethernet network applications and are used for running in walls and air plenums without the use of conduit. If you want to buy this kind of effective cable, I recommend you to visit Fiberstore, which offers fully typed OFNP fiber patch cables (SC, FC, LC, ST, MU, MTRJ, E2000, MTP etc) at only 3 dollars each.