When you design the cable, you should know the following criteria.
1. Pulling strength
Some cable is simply laid into cable trays or ditches, so pull strength is not too important. But other cable may be pulled thorough 2 km or more of conduit. Even with lots of cable lubricant, pulling tension can be high. Most cables get their strength from an aramid fiber (Kevlar is the duPont trade name), a unique polymer fiber that is very strong but does not stretch – so pulling on it will not stress the other components in the cable. The simplest simplex cable has a pull strength of 100-200 pounds, while outside plant cable may have a specification of over 800 pounds.
2.Water protection
Outdoors, every cable must be protected from water or moisture. It starts with a moisture resistant jacket, usually PE (polyethylene), and a filling of water-blocking material. The usual way is to flood the cable with a water-blocking gel. It’s effective but messy – requiring a gel remover (use the commercial stuff – it’s best- -but bottled lemon juice works in a pinch!). A newer alternative is dry water blocking using a miracle powder – the stuff developed to absorb moisture in disposable diapers. Check with your cable supplier to see if they offer it.
3. Fire code ratings
Every cable installed indoors must meet fire codes. That means the jacket must be rated for fire resistance, with ratings for general use, riser (a vertical cable feeds flames more than horizontal) and plenum (for installation in air-handling areas. Most indoor cables us PVC (polyvinyl chloride) jacketing for fire retardance. In the United States, all premises cables must carry identification and flammability ratings per the NEC (National Electrical Code) paragraph 770. These ratings are:
| NEC Rating | Description |
| OFN | Optical fiber Non-conductive |
| OFC | Optical fiber Conductive |
| OFNG or OFCG | General purpose |
| OFNR or OFCR | Riser rated cable for vertical runs |
| OFNP or OFCP | Plenum rated cables for use in air-handling plenums |
| OFN-LS | Low smoke density |
Cables without markings should never be installed as they will not pass inspections! Outdoor cables are not fire-rated and can only be used up to 50 feet indoors. If you need to bring an outdoor cable indoors, consider a double-jacketed cable with PE jacket over a PVC UL-rated indoor jacket. Simply remove the outdoor jacket when you come indoors and you will not have to terminate at the entry point. You can use an Indoor/Outdoor rated product with a Low Smoke Zero Halogen jacket.