What is Plenum Fiber Optic Cable?

plenum fiber cable

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Optical cables, as the “nervous system” for information exchange and transmission between buildings, have been laid in large numbers and concentrated in high-rise corridors/pipelines and shafts for optical fiber communication. However, in the event of a fire, these cables may contribute to the spread of the fire and make it more difficult to fight the fire. Therefore, plenum fiber optic cable came into being. Plenum fiber optic cable is also called OFNP optical cable. Plenum fiber cables utilize plastics around the fiber optic strands that utilize flame-retardant, low smoke materials. This cable offers high speed, high security, high fire rating and low smoke PVC or FEP compound. It can support an operating temperature from -25 to 125 degrees Celsius and is resistant to all kinds of chemicals.

What is a plenum fiber optic cable?
Plenum fiber optic cable or optic fiber non-conductive plenum (OFNP) is the National Fire Protection Association (NFPA) designation for indoor fiber optic cables that do not contain conductive components and are certified for use in plenum applications. Rated NEC 770 OFNP, plenum fiber optic cables are also called Communications Plenum Cables (CMP). Additionally, plenum fiber optic cable consists of a flame-retardant, low-smoke jacket that emits less smoke and is self-extinguishing. The fire retardant plastic jackets can be fluorinated ethylene polymer (FEP), polytetrafluoroethylene (PTFE), or low-smoke polyvinyl chloride (PVC). Plenum fiber optic cable is rated to run through an air plenum, such as the space above a drop ceiling.

What is Plenum Space?
A Plenum Space is a space that is used to return air back to the building’s air conditioning or heating system. Plenum-rated cabling has an outer jacket that, if exposed to extreme heat or open flame, will not release toxic gasses. Most building codes (hospitals, schools, residential, airports, and commercial buildings) specify that in plenum spaces and ducts, only plenum fiber optic cables can be used. Typically, a plenum is an open space above the suspended ceiling and below the raised floor. In most buildings with heating, ventilation, and air conditioning (HVAC) systems, air ducts supply air from outside HVAC units to the interior of the building, but the return air passes through the open space above the suspended ceiling, making it a plenum. These spaces are critical for air circulation, but due to the high airflow, they are likely to cause a potential fire hazard.

plenum space

What does OFNP Mean?
OFNP (Optical Fiber Nonconductive Plenum), NEC standard flame retardant grade (supercharged grade), the highest grade. Assuming that a fan is used to forcibly blow the flame to a bundle of flame-retardant (supercharged) optical fiber cables, the flame on the optical fiber cables will extinguish itself within 5 feet, and non-toxic and non-corrosive gases will be generated.

Features and Benefits
Plenum-rated cables typically have flammability requirements and outgassing requirements such that they won’t propagate and fire and won’t emit toxic smoke if they are burned. Additionally, the use of plenum fiber optic cable can help reduce network-cabling costs by making it easier to safely route cables through open spaces above ceilings.

A plenum fiber optic cable is a type of fiber optic cable that is designed for use in air-handling spaces. Plenum-rated fiber cable can be used in a riser space, but a riser cable generally cannot be used in a plenum space. That is to say, A plenum cable can be used in non-plenum areas, but a non-plenum cable cannot be used in plenum areas. Plenum cables have a fire-resistant jacket and are often used in commercial and industrial buildings.
Generally speaking, plenum fiber optic cable is suitable for use in horizontal wiring areas and inflated environments (conveying pipes, air handling systems), where the air is circulated and fires are difficult to control. Therefore, the use of OFNP flame-retardant grade fiber optic cables is the best choice. Because data centers of different sizes have different impacts after a fire occurs, the US NEC standard recommends optical fiber cables suitable for different environments. Generally, plenum fiber optic cable is suitable for use in large/ultra-large data centers, and fault-tolerant/parallel-maintainable data centers.
Nowadays, plenum distribution cable is used in trunking, LAN and distribution application. It has been widely applied in ducts, conduits, plenums and other spaces, as well as in building airflow, Gigabit Ethernet, broadband systems, telecommunications, data centers and indoor/outdoor environments.
data center plenum

Plenum fiber optic cable uses fluorocarbon jackets to provide low smoke and flame characteristics. This is the fiber optic cable with the highest fire rating, and no other type of fiber optic cable can be used as a substitute. With the continuous acceleration of urbanization, the number of public facilities such as high-rise buildings, subways, and commercial places continues to increase, and the safety hazards brought about by dense population and surge in electricity demand make plenum fiber optic cable an inevitable choice for safe communication.

Echo Huang

Echo Huang is an expert wordsmith and marketing professional at Bonelinks with more than 8 years of experience in high technology businesses – fiber optics, IoT, and telecommunication. She is very glad to share industry knowledge and communicate with others.

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