In the fiber optic industry we have all probably seen the words, plenum or riser in our day because these are two of the most common jacket types in the United States. But there are other options out there that are lesser known and talked about - such as Low Smoke Zero Halogen (LSZH), and Polyethylene (Pe).

When you look at the construction of any fiber optic cable, you will notice that the outer jacket is the first line of defense against chemicals, water, burning and other potentially damaging effects that could compromise the viability of the cable. Cable jackets come in multiple colors and there are industry standard color codes such as Aqua for OM3 or Yellow for Singlemode but in some cases there can be custom colored jackets. There are certain things you will see on the jacket such as foot markers that show you length of the cable, and a print string showing the type of fiber, manufacturer of the cable and the type of cable construction. Most cable jacket material is made from PVC or Polyvinyl Chloride, the additives to the PVC ultimately determine its jacket rating. Plenum and riser ratings are given by the National Electric Code (NEC). They are also responsible for the standards by which these cables must abide in order to be classified as plenum or riser cabling. This standard basically states that if a fire were to start within a structure, how much would these compounds contribute to the fire, and create a “fuel” source transporting the fire from place to place along the cable’s pathway, as well as the amount of toxic fumes that will be produced when the cable is burning. Most fiber optic cables that adhere to these fire standards are Underwriters Laboratories (UL) tested, meaning that they bear the UL mark on the cable jacket and they have been certified to meet the NEC Standard for the cable jacket type. These UL Listings are independently tested, and qualified to ensure that the safety measures are upheld. They (UL) have no monetary stake with the items that they test, and consumers can be assured that this UL listing means that the safety standards are being upheld. These listings are given, and can be taken away at any point if the quality of the product does not continue to meet the UL standard. The real question that many technicians ask in the field is where to use what type of jacketing. Below we will go into a breakdown of some cable jacket ratings and where they can be utilized within a building or structure.



Plenum Cable


Plenum has the highest fire rating, meaning that it can be installed within all of the plenum spaces in a building such as the air ducts and ventilation systems, basically any part of the building that has to do with heating or cooling air flow. Plenum can realistically be utilized in any space within a building as an alternative. Plenum cables are less hazardous and create less smoke in the case of fire. If a job requires plenum cable then plenum cable must be installed, there are no alternatives for this type of cable installation. Plenum cables for the above reasons are usually slightly more expensive than most other alternative cable jackets.



Riser Cable


Riser cabling is only to be used in riser spaces within a building such as in building shafts, for vertical runs. It is meant to be a backbone cable. The fire ratings that fit a riser rated cable are not as strict as plenum. You can utilize a plenum cable within a riser space, but you cannot utilize a riser cable in a plenum space. For example, in the case of a ventilation shaft, you cannot install a riser cable as this is a plenum air space, but you can install riser in an elevator shaft between the floors of a building. Typically, riser cables are less expensive than plenum because the standards are less stringent.



Low Smoke Zero Halogen (LSZH) Cable


Low Smoke Zero Halogen cable jacketing or LSZH is a separate classification from riser or plenum cables because it does not contain the same compounds or thermoplastics that produce smoke and other hazardous chemicals that could be harmful to humans and animals that might be in the vicinity of the cable, if it ever should burn. To be considered low smoke zero halogen cable, the PVC jacket must be made of flame retardant materials that do not excrete halogens and that also produce little to no smoke when it burns. LSZH is not the same as a plenum cable - they are two different fire ratings. While it may seem beneficial to use LSZH in every space in a building, this type of cable does not fit the bill for every single application. Since this jacket material is far more expensive than other compounds, it does not make sense to install this cable type in areas that do not require a less hazardous, or low smoke material. LSZH is highly recommended for areas that have poor ventilation, areas that people tend to congregate in or in a confined space. LSZH jackets are primarily utilized in Europe currently, but this type of cable is gaining traction in the US market.



PE Cable


PE (polyethylene) jackets are primarily used in outdoor rated cable jackets only; this is not cable that can be installed inside of buildings. PE cable’s superior weather and water resistance makes it a great pick for harsh weather conditions and installations, but its rigid characteristics make it difficult to utilize in environments that require flexibility or movement of the cable. This kind of cable jacket also boasts superior UV protection as its black coloring absorbs the sunlight, which is a typical characteristic of outdoor rated cabling.

While there are more cable ratings and classifications than the ones shown above, these are the most common types that your average technician will run into on the job more than once. Being familiar with the cable jacket ratings is a good piece of knowledge for an installation technician to have in his or her pocket. Knowing and being able to define what makes a plenum cable plenum or riser cable riser is superior knowledge that will benefit the tech on future jobs.