Fiber Optic Cable Specifications – A Primer

It is important to take a look at different options when it comes to wiring. It cannot be denied that we are moving to wireless in many areas, but wireless cannot match the speeds of a hard cable.

Within an office or a home, if you want to have good speeds, it is certainly worth looking at using fiber optic cables. A quality fiber optic cabling will ensure that your systems are linked together and work as they should. LAN wiring is important because it is designed to last. A lot of the time, certain companies may produce pieces of technology that are sub-standard. This may be due to negligence, or it may be due to the fact that they want to charge people more money. Whatever it happens to be, it is important to take a look at the options that are on offer when it comes to better quality cabling. A frequent complaint of many people who own iPods, MP3s and other digital media devices is that headphone wires tend to break very easily. Cheap versions will often require a user to buy a new pair every month or two, while better versions can end up lasting for years at a time.

Construction of Fiber Optic Cables

A fiber optic cable consists of two parts – core and cladding. The core is a small tube made of silica glass that carries the light rays that is covered by a cladding to ensure complete reflection. The cladding is usually coated with a layer of acrylate polymer or polyimide. Several layers of protective sheathing may be applied depending upon the application. Usually several of these cables are kept together with appropriate separators to form the cable that you see.

For outdoor application where weather plays a hand, more rigid and robust construction may be applied for protection. Modern cable can have upto 1000 fibers in a single cable giving you potential bandwidth of multiple terabytes per second!

Fiber Specifications

Specifications for fiber optics are a little complicated and can be divided into four categories – optical, mechanical, environmental, and dimensional.

Optical specs included attenuation, and bandwidth that are given as two wavelengths – 850 and 1,300 nm for multimode, and 1,310 and 1,550 for single mode. Mechanical specs include tensile strength and resistance to impact, crush, and twists. Environmental specs include temperature ranges for operation and storage, sensitivity to moisture and sunlight.

Electronic Industries Alliance (TIA/EIA-Arlington, VA) provide all the necessary requirements for a cable to meet set standards. There is also the IEEE-802.3z standard for Gigabit Ethernet, published by the IEEE-New York. A reference to one of these standards will provide all necessary details.

Cable Specifications

While the fiber specification ensures that performance standards are met, the fiber has to be properly encased in a protective covering that will protect it during operations. Indoor cables are designed for flexibility, tensile strength, ease of handling, and being flame resistant. Indoor cables must meet one of four listing categories of the National Electrical Code (NEC): OFN/OFC or OFNG/OFCG for general purpose, OFNR/OFCR for riser applications, and OFNP/OFCP for plenum areas.

Outdoor cables have stricter specs. They have to be designed to withstand a lifetime of 20 to 40 years. They must withstand wide operating temperatures, be resistant to sunlight and moisture, and have sufficient tensile strength for long draws. Waterblocking is also essential. Most outdoor cables have a loose jacket for isolation, and are filled with grease or gel to make them water resistant.

Outdoor cables that have to be buried also have to incorporate a steel tape armor for protection against rodents. For aerial installation, the cable must also have a messenger wire for lashing.

There is also the category called indoor/outdoor cables. These incorporate both the characteristics explained above.

A full cable specification has to include environmental and regulatory factors that include temperature, mechanical loading, moisture, sunlight, flammability, rodents, and chemicals.

The Insulated Cable Engineers Association (ICEA-South Yarmouth, MA) has published two documents that contain all the specs. These are ANSI/ICEA S-87-640 for Outside Plant Communications Cable, and the ANSI/ICEA S-83-596 for Fiber Optic Premises Distribution Cable.

The industry and industry standards have taken great effort to ensure that the standards are set for the design and manufacture of fiber optic cables. These standards are usually preceded by exhaustive tests that take a fiber optic cable to its breaking point.

As an end user what we have to do is to ensure that the cable we buy meet these standards. Purchasing cable from well-known brands is half the distance covered. But having knowledge on what to look for is important by itself.