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PVC vs LSZH vs OFNP vs OFNR Cable Jackets

What's the Difference between PVC, LSZH, OFNP, OFNR?

When comparing fiber optics cables, there are a lot of different components and considerations. One important component is the outer jacket of the cable. Outer jackets can be made from a number of materials, and generally speaking, the jacket materials can work with any fiber cable type. That means that choosing the right cable jacket is often independent of choosing the fiber setup.

Cable jackets mostly matter for meeting safety standards. Fiber cables often run through buildings and confined spaces. Because of that, they might be subjected to high-heat areas or poor ventilation. That is why they have fire safety ratings. Depending on where the cable runs and its application, there are regulations that might determine which jackets and fire safety ratings are required.

Jacket Materials

PVC

PVC cables are fairly common. It’s an affordable, accessible material for cable jackets. PVC is soft, and it resists oxidation, which helps it not burn terribly easily. That said, it has the worst fire rating of the four main types.

The main consideration with PVC is the list of byproducts produced when it does burn. It will give off black smoke, create hydrochloric acid, and release a number of toxic gasses. Clearly, that is undesirable.

Because of these risks, PVC is primarily used in ventilation systems that are completely contained. If the ventilation can account for the risks of PVC byproducts, then it can be safely used. Ventilation systems that lack such design elements cannot use PVC jackets.

When PVC is implemented, it is good for horizontal and vertical runs.

LSZH

LSZH stands for Low Smoke Zero Halogen. The name really says it all. This is a jacket that is designed to resist fire dangers, and as the name implies, this material produces very little smoke and no halogens when it burns.

It is more rigid than PVC and more flame-retardant. It is non-toxic when it burns. Because of that, it is favored in poorly ventilated areas, such as an airplane or subway car. LSZH is more expensive than most other jacket materials.

Safety Ratings

There are four levels of fire resistance for fiber cables and each level has two divisions which are the conductive and non-conductive cables. The higher rating cable is backward compatible with the lower rating cable and can be substituted while the lower rating cables can’t be used in place for the higher ratings.

  • OFNP
  • ONR
  • OFNG or OFGC
  • OFN or OFC

OFNG cables are designed for general purpose areas and have minimal fire prevention requirements (fire can’t go more than 4 feet and 11 inches). OFN cables are also general-purpose cables where the fire cannot infiltrate floors or ceilings. OFNR and OFNP cables are a little more specific and worth looking at in greater detail.

OFNR

OFNR stands for Optical Fiber Nonconductive Riser. This safety rating is usually given to PVC jackets. Cables with this rating are often used for vertical runs between buildings, but the applications are limited.

More generally, OFNR does not have smoke ratings. Because of that, it cannot be used in the ventilation area, regardless of the ventilation design. Outside of ventilation areas, OFNR cables are a popular choice because it is designed to save costs for cables in the riser.

OFNP

OFNP stands for Optical Fiber Nonconductive Plenum, and it sits on the opposite end of the spectrum from PVC. OFNP has the highest rating of any cable jacket. When regulations call for OFNP, there are no alternatives.

Because of this, OFNP is great for vertical runs in data centers. The cable jacket prevents the risk of fire burning along the cable from one floor to another, and it can run inside ventilation systems.

Cable Jacket Key Terms

Some of these comparisons are based on industry terms such as the plenum or the riser.

What is the Riser Area?

Examples of riser areas are floor openings, tubes, or channels that run upwards over one or more floors. Riser cable is planned for use in upright shafts that run between floors.

What is the General-Purpose Area?

A general-purpose area is all other areas that are not plenum or riser on the same space or floor.

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